Small models also found the vulnerabilities that Mythos found

https://aisle.com/blog/ai-cybersecurity-after-mythos-the-jagged-frontier

by dominicq • 3 months ago

1284 339 3 months ago

epistasis3• 3 months ago

We took the specific vulnerabilities Anthropic showcases in their announcement, isolated the relevant code, and ran them through small, cheap, open-weights models. Those models recovered much of the same analysis. Eight out of eight models detected Mythos's flagship FreeBSD exploit, including one with only 3.6 billion active parameters costing $0.11 per million tokens.

Impressive, and very valuable work, but isolating the relevant code changes the situation so much that I'm not sure it's much of the same use case.

Being able to dump an entire code base and have the model scan it is they type of situation where it opens up vulnerability scans to an entirely larger class of people.

odie5533• 3 months ago

Isn't the difference just harness then? I can write a harness that chunks code into individual functions or groups of functions and then feed it into a vulnerability analysis agent.

jcims• 3 months ago

It's probably not the 'only' difference, because clearly the models are advancing in capability, but it's likely way more important than generally given credit for.

elicash2• 3 months ago

This is from the first of the caveats that they list:

Scoped context: Our tests gave models the vulnerable function directly, often with contextual hints (e.g., "consider wraparound behavior"). A real autonomous discovery pipeline starts from a full codebase with no hints. The models' performance here is an upper bound on what they'd achieve in a fully autonomous scan. That said, a well-designed scaffold naturally produces this kind of scoped context through its targeting and iterative prompting stages, which is exactly what both AISLE's and Anthropic's systems do.

That's why their point is what the subheadline says, that the moat is the system, not the model.

Everybody so far here seems to be misunderstanding the point they are making.

wat100003• 3 months ago

If that’s the case, why didn’t they do it that way?

anotheryou• 3 months ago

huh, running it over each function in theory but testing just the specific ones here makes sense, but that hint?!

TacticalCoder2• 3 months ago

That's why their point is what the subheadline says, that the moat is the system, not the model.

Can you expand a bit more on this? What is the system then in this case? And how was that model created? By AI? By humans?

tehryanx3• 3 months ago

I get what you're saying, but I think this is still missing something pretty critical.

The smaller models can recognize the bug when they're looking right at it, that seems to be verified. And with AISLE's approach you can iteratively feed the models one segment at a time cheaply. But if a bug spans multiple segments, the small model doesn't have the breadth of context to understand those segments in composite.

The advantage of the larger model is that it can retain more context and potentially find bugs that require more code context than one segment at a time.

That said, the bugs showcased in the mythos paper all seemed to be shallow bugs that start and end in a single input segment, which is why AISLE was able to find them. But having more context in the window theoretically puts less shallow bugs within range for the model.

I think the point they are making, that the model doesn't matter as much as the harness, stands for shallow bugs but not for vulnerability discovery in general.

lelanthran• 3 months ago

That's why their point is what the subheadline says, that the moat is the system, not the model.

I'm skeptical; they provided a tiny piece of code and a hint to the possible problem, and their system found the bug using a small model.

That is hardly useful, is it? In order to get the same result , they had to know both where the bug is and what the bug is.

All these companies in the business of "reselling tokens, but with a markup" aren't going to last long. The only strategy is "get bought out and cash out before the bubble pops".

epistasis3• 3 months ago

If that's the point they are making, let's see their false positive rate that it produces on the entire codebase.

They measured false negatives on a handful of cases, but that is not enough to hint at the system you suggest. And based on my experiences with $$$ focused eval products that you can buy right now, e.g. greptile, the false positive rate will be so high that it won't be useful to do full codebase scans this way.

LordDragonfang4• 3 months ago

That said, a well-designed scaffold naturally produces this kind of scoped context through its targeting and iterative prompting stages, which is exactly what both AISLE's and Anthropic's systems do.

Unless the context they added to get the small model to find it was generated fully by their own scaffold (which I assume it was not, since they'd have bragged about it if it was), either they're admitting theirs isn't well designed, or they're outright lying.

People aren't missing the point, they're saying the point is dishonest.

scotty79• 3 months ago

Scoped context: Our tests gave models the vulnerable function directly, often with contextual hints (e.g., "consider wraparound behavior").

To be fair, nothing stops anyone from feeding each function of given codebase separately with one out of the predefined set of hints.

It's just AST and a for loop. Calling it a system is a bit much.

loire280• 3 months ago

Anthropic's own scaffold is described in their technical post: launch a container, prompt the model to scan files, let it hypothesize and test, use ASan as a crash oracle, rank files by attack surface, run validation. That is very close to the kind of system we and others in the field have built, and we've demonstrated it with multiple model families, achieving our best results with models that are not Anthropic's. The value lies in the targeting, the iterative deepening, the validation, the triage, the maintainer trust. The public evidence so far does not suggest that these workflows must be coupled to one specific frontier model.

The argument in the article is that the framework to run and analyze the software being tested is doing most of the work in Anthropic's experiment, and that you can get similar results from other models when used in the same way.

roywiggins5• 3 months ago

Maybe that's true, but they didn't actually show that that's true, since they didn't try scaffolding smaller models in a similar way at all.

Jcampuzano2• 3 months ago

The thing is with smaller cheaper models it is very possible to simply take every file in a codebase, and prompt it asking for it to find vulnerabilities.

You could even isolate it down to every function and create a harness that provides it a chain of where and how the function is used and repeat this for every single function in a codebase.

For some very large codebases this would be unreasonable, but many of the companies making these larger models do realistically have the compute available to run a model on every single function in most codebases.

You have the harness run this many times per file/function, and then find ones that are consistently/on average pointed as as possible vulnerability vectors, and then pass those on to a larger model to inspect deeper and repeat.

Most of the work here wouldn't be the model, it'd be the harness which is part of what the article alludes to.

loeg2• 3 months ago

it is very possible to simply take every file in a codebase, and prompt it asking for it to find vulnerabilities.

My understanding (based on the Security, Cryptography, Whatever podcast interview[0] -- which, by the way, go listen to it) is that this is actually what Anthropic did with the large model for these findings.

[0] https://securitycryptographywhatever.com/2026/03/25/ai-bug-f...

I wrote a single prompt, which was the same for all of the content management systems, which is, I would like you to audit the security of this codebase. This is a CMS. You have complete access to this Docker container. It is running. Please find a bug. And then I might give a hint. “Please look at this file.” And I’ll give different files each time I invoke it in order to inject some randomness, right? Because the model is gonna do roughly the same time each time you run it. And so if I want to have it be really thorough, instead of just running 100 times on the same project, I’ll run it 100 times, but each time say, “Oh, look at this login file, look at this other thing.” And just enumerate every file in the project basically.

roywiggins5• 3 months ago

"small models can do this if you scaffold them right" might be true, but it wasn't actually demonstrated in the post.

MaxLeiter• 3 months ago

I think they key thing here is they "isolated the relevant code"

If the exploits exist in e.g. one file, great. But many complex zerodays and exploits are chains of various bugs/behaviors in complex systems.

Important research but I don’t think it dispels anything about Mythos

slopinthebag3• 3 months ago

Did Mythos identify vulnerabilities across files? Afaik Mythos worked the same way, analysing a single file at a time.

davebren4• 3 months ago

Seems perfectly comparable to anthropic's method, they just wrapped the same kind of prompt in a for loop.

JackYoustra2• 3 months ago

Isolated the relevant code

I mean isn't that most of it? If you put a snippet of code in front of me and said "there's probably a vulnerability here" I could probably spend a few hours (a much lower METR time!) and find it. It's a whole other ballgame to ask me with no context to come up with an exploit.

kennywinker4• 3 months ago

Sure. But it’s a computer. You can run “there’s probably a vulnerability here” as many times as you like. And it’s easier and cheaper to run it many times with a small open model than a big frontier model.

It also sounds like that is how mythos works too. Which makes sense - the linux kernel is too big to fit in context

JackYoustra2• 3 months ago

No, it sounds like mythos is just doing parallel trajectories. that's pretty distinct!

amazingamazing3• 3 months ago

Did mythos isolate the code to begin with? Without a clear methodology that can be attempted with another model the whole thing is meaningless

aniceperson• 3 months ago

to be fair, last post i saw from anthropic on finding linux kernel vulnerability was a while loop per failed prompting "there is a vulnerability here, find it" more important than that, no frontier model can keep the entire linux kernel in context, so there definitely is code isolation, either explicitly or implicitly (the model itself delegates subagents with smaller chunks of code)

loeg2• 3 months ago

No. How would it? Before the vulns were identified by Mythos, no one knew what the relevant portion to isolate was.

bhouston3• 3 months ago

They did do one agent per code chunk, yes. But key is that their agent had to identify when there was a vulnerability and when there wasn't. This "small model" test only had to label the known positive cases as positive -- which any function that simply returns "true" can do. This whole test setup is annoying because it proves nothing.

dist-epoch• 3 months ago

Anthropic claim is not necessarily that Mythos found vulnerabilities that other models couldn't but that it could easily exploit them while previous models failed to do that:

“Opus 4.6 is currently far better at identifying and fixing vulnerabilities than at exploiting them.” Our internal evaluations showed that Opus 4.6 generally had a near-0% success rate at autonomous exploit development. But Mythos Preview is in a different league. For example, Opus 4.6 turned the vulnerabilities it had found in Mozilla’s Firefox 147 JavaScript engine—all patched in Firefox 148—into JavaScript shell exploits only two times out of several hundred attempts. We re-ran this experiment as a benchmark for Mythos Preview, which developed working exploits 181 times, and achieved register control on 29 more.

rychu• 3 months ago

If that was normal Opus, then it sounds to me like Mythos could be a big model, instruction tuned, but without all the safety/refusal part of training.

chirau• 3 months ago

Their isolation approach is totally different from Mythos approach though. Mythos had to evaluate whole code bases rather than isolated sections. It's like saying one dog walked into the Amazon jungle and found a tennis ball and then another team isolated a 1 square kilometer radius that they knew the ball was definitely in and found the same ball.

kennywinker4• 3 months ago

I don’t think mythos can ingest an entire codebase into context. So it’s spinning off sub-agents to process chunks. Which supports their thesis: the harness is the moat. The tooling is whats important, the model is far far less important.

bhouston3• 3 months ago

Mythos was clear it was one agent per chunk. But this positive confirming results do not actually disprove anytime with Mythos, because it is only one side of the discriminator challenge - you got positives, but we do not know your false positive rate and your false negative rate.

eiens3• 3 months ago

Let’s suppose that’s true

What’s so special about the harness - why wouldn’t others be able to replicate it?

hakanderyal• 3 months ago

Even that would be more meaningful test. They basically coated the ball with a strong smell, then they prepped the dog with that smell, then set it loose in a 5x5 meter area.

"Our tests gave models the vulnerable function directly, often with contextual hints (e.g., "consider wraparound behavior")."

johnfn10• 3 months ago

The Anthropic writeup addresses this explicitly:

This was the most critical vulnerability we discovered in OpenBSD with Mythos Preview after a thousand runs through our scaffold. Across a thousand runs through our scaffold, the total cost was under $20,000 and found several dozen more findings. While the specific run that found the bug above cost under $50, that number only makes sense with full hindsight. Like any search process, we can't know in advance which run will succeed.

Mythos scoured the entire continent for gold and found some. For these small models, the authors pointed at a particular acre of land and said "any gold there? eh? eh?" while waggling their eyebrows suggestively.

For a true apples-to-apples comparison, let's see it sweep the entire FreeBSD codebase. I hypothesize it will find the exploit, but it will also turn up so much irrelevant nonsense that it won't matter.

SoftTalker2• 3 months ago

How much of that is simply scale? Anthropic threw probably an entire data center at analyzing a code base. Has anyone done the same with a "small" model?

jstanley• 3 months ago

It's still useful if $20k of consultants would be less effective.

hellcow• 3 months ago

It seems feasible to use a small/cheap model to flag possible vulnerabilities, and then use a more expensive model to do a second-pass to confirm those, rather than on every file. Could dramatically reduce the total cost and speed up the process.

conception• 3 months ago

Does it? I don’t see quality from small models being high enough to be able to effectively scour a code based like this.

notnullorvoid• 3 months ago

I hypothesize it will find the exploit, but it will also turn up so much irrelevant nonsense that it won't matter.

The trick with Mythos wasn't that it didn't hallucinate nonsense vulnerabilities, it absolutely did. It was able to verify some were real though by testing them.

The question is if smaller models can verify and test the vulnerabilities too, and can it be done cheaper than these Mythos experiments.

iririririr• 3 months ago

so it's just better at hallucinations, but they added discrete code that works as a fuzzer/verifier?

bredren• 3 months ago

The article positions the smaller models as capable under expert orchestration, which to be any kind of comparable must include validation.

hibikir• 3 months ago

People often undervalue scaffolding. I was looking at a bug yesterday, reported by a tester. He has access to Opus, but he's looking through a single repo, and Amazon Q. It provided some useful information, but the scaffolding wasn't good enough.

I took its preliminary findings into Claude Code with the same model. But in mine it knows where every adjacent system is, the entire git history, deployment history, and state of the feature flags. So instead of pointing at a vague problem, it knew which flag had been flipped in a different service, see how it changed behavior, and how, if the flag was flipped in prod, it'd make the service under testing cry, and which code change to make to make sure it works both ways.

It's not as if a modern Opus is a small model: Just a stronger scaffold, along with more CLI tools available in the context.

The issue here in the security testing is to know exactly what was visible, and how much it failed, because it makes a huge difference. A middling chess player can find amazing combinations at a good speed when playing puzzle rush: You are handed a position where you know a decisive combination exist, and that it works. The same combination, however, might be really hard to find over the board, because in a typical chess game, it's rare for those combinations to exist, and the energy needed to thoroughly check for them, and calculate all the way through every possible thing. This is why chess grandmasters would consider just being able to see the computer score for a position to be massive cheating: Just knowing when the last move was a blunder would be a decisive advantage.

When we ask a cheap model to look for a vulnerability with the right context to actually find it, we are already priming it, vs asking to find one when there's nothing.

celeritascelery• 3 months ago

That was my thought exactly. If small models can find these same vulnerabilities, and your company is trying to find vulnerabilities, why didn’t you find them?

rakejake• 3 months ago

Maybe they did use small models but you couldn't make the front page of HN with something like this until Anthropic made a big fuss out of it. Or perhaps it is just a question of compute. Not everyone has 20k$ or the GPU arsenal to task models to find vulnerabilities which may/may not be correct?

Unless Anthropic makes it known exactly what model + harness/scaffolding + prompt + other engineering they did, these comparisons are pointless. Given the AI labs' general rate of doomsday predictions, who really knows?

echelon• 3 months ago

Who is spending millions of dollars on small models to find vulns? Nobody else is selling here or has the budget to sell quite like this.

Anthropic spends millions - maybe significantly more.

Then when they know where they are, they spend $20k to show how effective it is in a patch of land.

They engineered this "discovery".

What the small teams are doing is fair - it's just a scaled down version of what Anthropic already did.

petters• 3 months ago

They have found a large number in OpenSSl

jerf• 3 months ago

I speculatively fired Claude Opus 4.6 at some code I knew very well yesterday as I was pondering the question. This code has been professionally reviewed about a year ago and came up fairly clean, with just a minor issue in it.

Opus "found" 8 issues. Two of them looked like they were probably realistic but not really that big a deal in the context it operates in. It labelled one of them as minor, but the other as major, and I'm pretty sure it's wrong about it being "major" even if is correct. Four of them I'm quite confident were just wrong. 2 of them would require substantial further investigation to verify whether or not they were right or wrong. I think they're wrong, but I admit I couldn't prove it on the spot.

It tried to provide exploit code for some of them, none of the exploits would have worked without some substantial additional work, even if what they were exploits for was correct.

In practice, this isn't a huge change from the status quo. There's all kinds of ways to get lots of "things that may be vulnerabilities". The assessment is a bigger bottleneck than the suspicions. AI providing "things that may be an issue" is not useless by any means but it doesn't necessarily create a phase change in the situation.

An AI that could automatically do all that, write the exploits, and then successfully test the exploits, refine them, and turn the whole process into basically "push button, get exploit" is a total phase change in the industry. If it in fact can do that. However based on the current state-of-the-art in the AI world I don't find it very hard to believe.

It is a frequent talking point that "security by obscurity" isn't really security, but in reality, yeah, it really is. An unknown but presumably staggering number of security bugs of every shape and size are out there in the world, protected solely by the fact that no human attacker has time to look at the code. And this has worked up until this point, because the attackers have been bottlenecked on their own attention time. It's kind of just been "something everyone knows" that any nation-state level actor could get into pretty much anything they wanted if they just tried hard enough, but "nation-state level" actor attention, despite how much is spent on it, has been quite limited relative to the torrent of software coming out in the world.

Unblocking the attackers by letting them simply purchase "nation-state level actor"-levels of attention in bulk is huge. For what such money gets them, it's cheap already today and if tokens were to, say, get an order of magnitude cheaper, it would be effectively negligible for a lot of organizations.

In the long run this will probably lead to much more secure software. The transition period from this world to that is going to be total chaos.

... again, assuming their assessment of its capabilities is accurate. I haven't used it. I can't attest to that. But if it's even half as good as what they say, yes, it's a huge huge huge deal and anyone who is even remotely worried about security needs to pay attention.

alpha_squared• 3 months ago

This is addressed elsewhere in the comments, but it appears this is actually a direct comparison to how Anthropic got their Mythos headline results.

https://news.ycombinator.com/item?id=47732322

Aurornis2• 3 months ago

How is that a direct comparison? The link you gave has a quote that says it’s not:

Scoped context: Our tests gave models the vulnerable function directly, often with contextual hints (e.g., "consider wraparound behavior"). A real autonomous discovery pipeline starts from a full codebase with no hints

They pointed the models at the known vulnerable functions and gave them a hint. The hint part is what really breaks this comparison because they were basically giving the model the answer.

yorwba2• 3 months ago

We don't even need to hypothesize that much on the irrelevant nonsense, since they helpfully provide data with the detected vulnerability patched: https://aisle.com/blog/ai-cybersecurity-after-mythos-the-jag... and half of the small models they touted as finding the vulnerability still found it in the patched code in 3/3 runs. A model that finds a vulnerability 100% of the time even when there is none is just as informative as a model that finds a vulnerability 0% of the time even when there is one. You could replace it with a rock that has "There's a vulnerability somewhere." engraved on it.

They're a company selling a system for detecting vulnerabilities reliant on models trained by others, so they're strongly incentivized to claim that the moat is in the system, not the model, and this post really puts the thumb on the scale. They set up a test that can hardly distinguish between models (just three runs, really??) unless some are completely broken or work perfectly, the test indeed suggests that some are completely broken, and then they try to spin it as a win anyway!

A high false-positive rate isn't necessarily an issue if you can produce a working PoC to demonstrate the true positives, where they kinda-sorta admit that you might need a stronger model for this (a.k.a. what they can't provide to their customers).

Overall I rate Aisle intellectually dishonest hypemongers talking their own book.

kilpikaarna• 3 months ago

Wasn't the scaffolding for the Mythos run basically a line of bash that loops through every file of the codebase and prompts the model to find vulnerabilities in it? That sounds pretty close to "any gold there?" to me, only automated.

Have Anthropic actually said anything about the amount of false positives Mythos turned up?

FWIW, I saw some talk on Xitter (so grain of salt) about people replicating their result with other (public) SotA models, but each turned up only a subset of the ones Mythos found. I'd say that sounds plausible from the perspective of Mythos being an incremental (though an unusually large increment perhaps) improvement over previous models, but one that also brings with it a correspondingly significant increase in complexity.

So the angle they choose to use for presenting it and the subsequent buzz is at least part hype -- saying "it's too powerful to release publicly" sounds a lot cooler than "it costs $20000 to run over your codebase, so we're going to offer this directly to enterprise customers (and a few token open source projects for marketing)". Keep in mind that the examples in Nicholas Carlini's presentation were using Opus, so security is clearly something they've been working on for a while (as they should, because it's a huge risk). They didn't just suddenly find themselves having accidentally created a super hacker.

johnfn10• 3 months ago

Wasn't the scaffolding for the Mythos run basically a line of bash that loops through every file of the codebase and prompts the model to find vulnerabilities in it? That sounds pretty close to "any gold there?" to me, only automated.

But the entire value is that it can be automated. If you try to automate a small model to look for vulnerabilities over 10,000 files, it's going to say there are 9,500 vulns. Or none. Both are worthless without human intervention.

I definitely breathed a sigh of relief when I read it was $20,000 to find these vulnerabilities with Mythos. But I also don't think it's hype. $20,000 is, optimistically, a tenth the price of a security researcher, and that shift does change the calculus of how we should think about security vulnerabilities.

omcnoe2• 3 months ago

Difference is the scaffold isn’t “loop over every file” - it’s loop over every discovered vulnerable code snippet.

If you isolate the codebase just the specific known vulnerable code up front it isn’t surprising the vulnerabilities are easy to discover. Same is true for humans.

Better models can also autonomously do the work of writing proof of concepts and testing, to autonomously reject false positives.

slashdave• 3 months ago

Signal to noise

leiyu19880522• 3 months ago

Been building AI coding tools for a while. The false positive problem is real - we had a user report every console.log flagged as security issue. Small models can work with very specific prompting and domain training data.

eichin• 3 months ago

That was the scaffolding for the Claude 4.6 run discussed here https://news.ycombinator.com/item?id=47633855 - if that's all it takes, dealing with Mythos is way too late :-)

nottorp• 3 months ago

Have Anthropic actually said anything about the amount of false positives Mythos turned up?

What? You want honest "AI" marketing?

Would you also like them to tell you how much human time was spent reviewing those found vulnerabilities before passing them on? And an unicorn delivered on Mars?

adam_patarino• 3 months ago

Anthropic has had the chance to explain what they did rationally. Instead they chose to be opaque and grandiose.

Giving them the benefit of the doubt is no longer appropriate.

asasidh• 3 months ago

yes their scaffold was a variation of claude - -dangerously-skip-permissions - p "You are playing in a CTF. Find a vulnerability. hint: look in src folder. Write the most serious one to ./va/report.txt." --verbose

letitgo12345• 3 months ago

Can't you execute the bug to see if the vulnerability is real? So you have a perfect filter. Maybe Mythos decided w/o executing but we don't know that.

cyanydeez6• 3 months ago

so what you're saying is no one could ever write a loop like:

for githubProject in githubProjects opencode command /findvulnerability end for

Seems like a silly thing to try and back up.

tredre32• 3 months ago

What he's saying is that you should read the "Caveats and limitations" section of the article.

Here's the first one:

Our tests gave models the vulnerable function directly, often with contextual hints (e.g., "consider wraparound behavior").

Mythos did no such thing, it was cut lose and told to find vulnerabilities. If the intent was to prove that small models are just as good, they haven't demonstrated that at all. The end.

WhyNotHugo• 3 months ago

OTOH, this article goes too far the opposite extreme:

We isolated the vulnerable svc_rpc_gss_validate function, provided architectural context (that it handles network-parsed RPC credentials, that oa_length comes from the packet), and asked eight models to assess it for security vulnerabilities.

To follow your analogy, they pointed to the exact room where the gold was hidden, and their model found it. But finding the right room within the entire continent in honestly the hard part.

mattmanser3• 3 months ago

Or would it have any way if they hadn't pointed it at it? Who knows?

Just like people paid by big tobacco found no link to cancer in cigarettes, researchers paid for by AI companies find amazing results for AI.

Their job literally depends on them finding Mythos to be good, we can't trust a single word they say.

hoppp• 3 months ago

They pay me 20k and give me time maybe I find it also.

LordDragonfang4• 3 months ago

No, you wouldn't. The vulnerability has been in the codebase for 17 years. Orders of magnitude more than 20k in security professional salary-hours have been pointed at the FreeBSD codebase over the past decade and a half, so we already know a human is unlikely to have found it in any reasonable amount of time.

glerk2• 3 months ago

I'm having trouble finding this info (I assume they won't publish it), but could the secret sauce be much larger and more readily accessible context window?

OpenBSD's code is in the 10s of millions of lines. Being able to hold all of it in context would make bug finding much easier.

johnfn10• 3 months ago

You can look at some of the bugs, if you'd like. They are (at least the ones I looked at) fairly self-contained, scoped to a single function, a hundred lines or less. There's no need for a massive amount of context.

lukev• 3 months ago

This is a really interesting point though -- it's really scaffold-dependent.

Because for the same price, you could point the small model at each function, one by one, N times each, across N prompts instructing it to look for a specific class of issue.

It's not that there's no difference between models, but it's hard to judge exactly how much difference there is when so much depends on the scaffold used. For a properly scientific test, you'd need to use exactly the same one.

Which isn't possible when Anthropic won't release the model.

lmeyerov• 3 months ago

Instead of scanning more code, afaict what you seem to want is instead, scan on the same small area, and compare on how many FPs are found there. A common measure here is what % of the reported issues got labeled as security issues and fixed. I don't see Mythos publishing on relative FP rate, so dunno how to compare those. Maybe something substantively changed?

At the same time, I'm not sure that really changes anything because I don't see a reason to believe attacks are constrained by the quality of source code vulnerability finding tools, at least for the last 10-15 years after open source fuzzing tools got a lot better, popular, and industrialized.

This might sound like a grumpy reply, but as someone on both sides here, it's easy to maintain two positions:

1. This stuff is great, and doing code reviews has been one of my favorite claude code use cases for a year now, including security review. It is both easier to use than traditional tools, and opens up higher-level analysis too.

2. Finding bugs in source code was sufficiently cheap already for attackers. They don't need the ease of use or high-level thing in practice, there's enough tooling out there that makes enough of these. Likewise, groups have already industrialized.

There's an element of vuln-pocalypse that may be coming with the ease of use going further than already happening with existing out-of-the-box blackbox & source code scanning tools . That's not really what I worry about though.

Scarier to me, instead, is what this does to today's reliance on human response. AI rapidly industrializes what how attackers escalate access and wedge in once they're in. Even without AI, that's been getting faster and more comprehensive, and with AI, the higher-level orchestration can get much more aggressive for much less capable people. So the steady stream of existing vulns & takeovers into much more industrialized escalations is what worries me more. As coordination keeps moving into machine speed, the current reliance on human response is becoming less and less of an option.

rakel_rakel2• 3 months ago

Spending $20000 (and whatever other resources this thing consumes) on a denial of service vulnerability in OpenBSD seems very off balance to me.

Given the tone with which the project communicates discussing other operating systems approaches to security, I understand that it can be seen as some kind of trophy for Mythos. But really, searching the number of erratas on the releases page that include "could crash the kernel" makes me think that investing in the OpenBSD project by donating to the foundation would be better than using your closed source model for peacocking around people who might think it's harder than it is to find such a bug.

paulddraper3• 3 months ago

You don’t see the value of vulnerabilities as on the order of 20k USD?

When it’s a security researcher, HN says that’s a squalid amount. But when its a model, it’s exorbitant.

theptip• 3 months ago

It’s $20k for all the vulns found in the sweep, not just that one.

And last security audit I paid for (on a smaller codebase than OpenBSD) was substantially more than $20k, so it’s cheaper than the going price for this quality of audit.

adampunk• 3 months ago

20,000 is the most this will ever cost.

andy_ppp• 3 months ago

I wonder if you could just setup a small model and suggest a load of things and try every file and it might still end up being cheaper and just as good as Mythos at a specific task. Maybe this will be something that holds true for more things, formulating a small model to do specific things may well end up being as effective/efficient as a larger model looking at a huge solution space.

davemp• 3 months ago

Across a thousand runs through our scaffold, the total cost was under $20,000

Lots of questions about the $20k. Is that raw electricity costs, subsidized user token costs? If so, the actual costs to run these sorts of tasks sustainably could be something like $200k. Even at $50k, a FreeBSD DoS is not an extremely competitive price. That's like 2-4mo of labor.

Don't get me wrong, I think this seems like a great use for LLMs. It intuitively feels like a much more powerful form of white box fuzzing that used techniques like symbolic execution to try to guide execution contexts to more important code paths.

Sparkyte• 3 months ago

Why not just write many small models for explicit tasks than running one bigger model anyway? I prefer the agentic subject matter expert design anyway. I suppose because it wants to look at the whole code base?

klempner• 3 months ago

The broad answer to the "irrelevant nonsense" for something like this is to use more expensive models to validate.

You don't need a model with a false positive rate that's good enough to not waste my time -- you just need one that's good enough to not waste the time (tokens) of Mythos or whatever your expensive frontier model is. Even if it's not, you have the option of putting another layer of intermediate model in the middle.

mlmonkey2• 3 months ago

We can reduce this to an even more basic question: if these small models are equally comparable in finding vulnerabilities, why haven't they done so yet?. After all, the source code is out in the open, and has been for decades. Please go ahead, find (and report) the vulnerabilities.

shmagadee• 3 months ago

I've read this statement a bunch of times and am still unclear what it is saying. It could mean: - The entire set of thousands of "findings" was generated with $20k worth of runs (have seen this in press publications and many user posts online). - The only the OpenBSD specific findings were generated with $20k - Some other subset of findings associated with a specific run configuration were generated with $20k?

I've also asked several LLMs to parse the wording for more clarity without success. They all highlight it as ambiguous wording. Why not use more direct language and provide the supporting data? They also stated that they are providing $100M in credits to their partners. So if bullet 1 or 2 are the meaning and "findings" scale linearly with cost, we're talking either millions (100M/20k * 1k+ findings) or hundreds of thousands. Does that make any sense? Or is the idea that all of these companies will run scans across their critical codebases continuously? Anyone else have a better sense of the math going on here?

AbstractH242• 3 months ago

So the real learning here is the cost of “using” GenAI to do things is declining at a rapid speed.

We’re not doing anything that couldn’t be done before, we’re just doing it faster, easier and cheaper.

Sounds like a recipe for a lot of junk being built. Also sounds like something that’s been true since the beginning of humanity.

In the more near term, sounds like a reminder the datacenters and processing boom will look at lot like the fiber one.

coldtea4• 3 months ago

Mythos scoured the entire continent for gold and found some. For these small models, the authors pointed at a particular acre of land and said "any gold there? eh? eh?" while waggling their eyebrows suggestively.

Which sounds trivial for a hacker wanting to find vulnerabilities to replicate, so what's the huge advantage of Mython then? That you don't need to spend 5 minutes to nudge it to the most complex/ripe for vulnerabilities parts of a codebase?

antirez• 3 months ago

Congrats: completely broken methodology, with a big conflict of interest. Giving specific bug hints, with an isolated function that is suspected to have bugs, is not the same task, NOR (crucially) is a task you can decompose the bigger task into. It is basically impossible to segment code in pieces, provide pieces to smaller models, and expect them to find all the bugs GPT 5.4 or other large models can find. Second: the smarter the model, and less the pipeline is important. In the latest couple of days I found tons if Redis bugs with a three prompts open-ended pipeline composed of a couple of shell scripts. Do you think I was not already tying with weaker models? I did, but it didn't work. Don't trust what you read, you have access to frontier models for 20$ a month. Download some C code, create a trivial pipeline that starts from a random file and looks for vulnerabilities, then another step that validates it under a hard test, like ASAN crash, or ability to reach some secret, and so forth, and only then the problem can be reported. Test yourself what it is possible. Don't let your fear make you blind. Also, there is a big problem that makes the blog post reasoning not just weak per se, but categorically weak: if small model X can find 80% of vulnerabilities, if there is a model Y that can find the other potential 20%, we need "Y": the maintainers should make sure they access to models that are at least as good as the black hats folks.

nsbsbdjdididi• 3 months ago

Thanks Dario, very cool!

Departed7405• 3 months ago

Exactly, this is so flawed. Anthropic themselves said they only reported <1% of the vulnerabilities found, cause the rest is unpatched.

Give open models an environment (prior to Feb 15- so no Mythos-discovered vulns are patche) of Linux and see how many vulnerabilities it can find. Then put it in a sandbox and see if it can escape and send you an e-mail.

slopinthebag3• 3 months ago

Idk, it seems reasonable to me

"Our tests gave models the vulnerable function directly, often with contextual hints. A real autonomous discovery pipeline starts from a full codebase with no hints. The models' performance here is an upper bound on what they'd achieve in a fully autonomous scan. That said, a well-designed scaffold naturally produces this kind of scoped context through its targeting and iterative prompting stages, which is exactly what both AISLE's and Anthropic's systems do."

Also they included a test with a false positive, the small models got it right and Opus got it wrong. So this paper shows with the right approach and harness these smaller models can produce the same results. Thats awesome!

So, if you're struggling to make these smaller models work it's almost certainly an issue of holding them wrong. They require a different approach/harness since they are less capable of working with a vague prompt and have a smaller context, but incredibly powerful when wielded by someone who knows how to use them. And since they are so fast and cheap, you can use them in ways that are not feasible with the larger, slower, more expensive models. But you have to know how to use them, it requires skill unlike just lazily prompting Claude Code, however the results can be far better. If you aren't integrating them in your workflow you're ngmi imo :) This will be the next big trend, especially as they continue to improve relative to SOTA which is running into compute limitations.

felipeerias2• 3 months ago

Anthropic gave the model the whole codebase and told it to find a vulnerability on a specific file, iterating across sessions focusing on different files.

What happens then is that, for example, the model looks through that particular file, identifies potential problems, and works upwards through the codebase to check whether those could actually be hit.

“Hum, here we assume that the input has been validated, is there any way that might not be the case?”

This is not unique to Mythos. You can already do this with publicly available models. Mythos does appear to be significantly more capable, so it would get better results.

The research discussed here provided models with just a known buggy function, missing the whole process required to find that bug in the first place.

woodruffw• 3 months ago

Those models recovered much of the same analysis

This is an essentially unquantifiable statement that makes the underlying claim harder to believe as an external party. What does “much” mean here? The end state of vulnerability exploitation is typically eminently quantifiable (in the form of a functional PoC that demonstrates an exploited end state), so the strong version of the claims here would ideally be backed up by those kinds of PoCs.

(Like other readers, I also find the trick of pre-feeding the smaller models the “relevant” code to be potentially disqualifying in a fair comparison. Discovering the relevant code is arguably one of the hardest parts of human VR.)

Retr0id• 3 months ago

And what about the false-positive rate?

dataflow• 3 months ago

Yeah, this is the critical question. If the model ends up flagging too much, that could end up being like a manual read of the code.

tptacek6• 3 months ago

If you cut out the vulnerable code from Heartbleed and just put it in front of a C programmer, they will immediately flag it. It's obvious. But it took Neel Mehta to discover it. What's difficult about finding vulnerabilities isn't properly identifying whether code is mishandling buffers or holding references after freeing something; it's spotting that in the context of a large, complex program, and working out how attacker-controlled data hits that code.

It's weird that Aisle wrote this.

ctoth2• 3 months ago

It's weird that Aisle wrote this.

No, writing an advertisement is not weird. What's weird is that it's top of HN. Or really, no, this isn't weird either if you think about it -- people lookin for a gotcha "Oh see, that new model really isn't that good/it's surely hitting a wall/plateau any day now" upvoted it.

goekjclo• 3 months ago

It's not weird. Top of HN is worthless as a barometer at this point, people downvote for calling out AI slop.

sanex• 3 months ago

Nah, Saturday post. Less news less content.

kennywinker4• 3 months ago

If it’s obvious when you look close, then automate looking close. Seems simple to write tools that spider thru a code base, finding logical groupings and feeding them into an LLM with prompts like “there is a vulnerability in this code, find it”.

The thesis is, the tooling is what matters - the tools (what they call the harness) can turn a dumb llm into a smart llm.

roywiggins5• 3 months ago

Right, but they didn't actually test that, did they?

tptacek6• 3 months ago

Hold on, I misread your comment because I'm knee-jerk about code scanners, which were the bane of my existence for a while. Reworking... and: done. The original comment was just the first graf without the LLM qualification. Sorry about that.

The general approach without LLMs doesn't work. 50 companies have built products to do exactly what you propose here; they're called static application security testing (SAST) tools, or, colloquially, code scanners. In practice, getting every "suspicious" code pattern in a repository pointed out isn't highly valuable, because every codebase is awash in them, and few of them pan out as actual vulnerabilities (because attacker-controlled data never hits them, or because the missing security constraint is enforced somewhere else in the call chain).

Could it work with LLMs? Maybe? But there's a big open question right now about whether hyperspecific prompts make agents more effective at finding vulnerabilities (by sparing context and priming with likely problems) or less effective (by introducing path dependent attractors and also eliminating the likelihood of spotting vulnerabilities not directly in the SAST pattern book).

SoftTalker2• 3 months ago

It's also that humans are very bad at repetitive detailed tasks. Sitting down with a code base and looking at each function for integer overflow comparison bugs gets boring really fast. It's a rare person who can do that for as long as it takes to find a bug that they don't already have some clues about.

It's the flaw in the "given enough eyeballs, all bugs are shallow" argument. Because eyeballs grow tired of looking at endless lines of code.

Machines on the other hand are excellent at this. They don't get bored, they just keep doing what they are told to do with no drop-off in attention or focus.

____tom____• 3 months ago

And there aren't enough security researchers in the world to review ALL the files from OpenBSD.

And if there were, the cost would be more like $20M than 20K.

Having all code reviewed for security, by some level of LLM, should be standard at this point.

throwatdem12311• 3 months ago

idk man, pay me enough money and I’ll look at as much code as you want looking for integer overflows

Would it be cheaper than Claude Mythos doing it? No idea. Maybe, maybe not.

But it’s weird how we’re willing to throw away money to a megacorp to do it with “automation” for potentially just as much if not more as it would cost to just have big bounty program or hiring someone for nearly the same cost and doing it “normally”.

It would really have to be substantially less cost for me to even consider doing it with a bot.

drc500free• 3 months ago

It’s like not differentiating between solving and verifying.

“PKI is easy to break if someone gives us the prime factors to start with!”

tombert• 3 months ago

It's weird, because when working on a big project, taking a break for a week or two, and returning to it, I will find a bug and will see hundreds of lines of code that are absolutely terrible, and I will tell myself "Tom you know better than to do this, this is a rookie mistake".

I think people forget that it's hard to be clever and tidy 100% of the time. Big programs take a lot of discipline and an understanding of the context that can be really hard to maintain. This is one of several reasons that my second draft or third draft of code is almost always considerably better than the first draft.

AbstractH242• 3 months ago

I think people forget that it's hard to be clever and tidy 100% of the time

People on the outside with imposter syndrome also need to remember this.

Any mature codebase is a bit messy.

tucnak• 3 months ago

The point of contention is whether Mythos is the product of its intelligence or its harness; the results like this, and other similar testimonies, call into question too-dangerous-to-release marketing, and for good reason, too. Because it is powerful marketing. Aisle merely says the intelligence is there in the small models. I say, it's already clear that competent defenders could viably mimic, or perhaps even eclipse what Mythos does, by (a) making better harness, (b) simply spending more on batch jobs, bootstrapping, cache better, etc. You may not be doing this yourself, but your probably should.

tptacek6• 3 months ago

Aisle and Anthropic are literally talking about two different problem spaces.

windexh8er2• 3 months ago

What's weird is that Google, Anthropic and OpenAI are claiming the model is the powerhouse, when what Aisle is stating is very much not the case.

It almost seems like a coordinated effort (Google in January, Anthropic and OAI in April) building out gated models that will eventually be very expensive. Yet, here we are: Aisle is saying that's not required to get there.

I don't think it's weird at all. It seems to me the Frontier providers are just trying to find, still unsuccessfully, a moat to make their unsustainable business model... Well. Sustainable.

bloppe• 3 months ago

I agree that the apocalyptic messaging about mythos is eye-rolling, but the thesis of the article that "the moat is the system, not the model" is weird because the point is that the model is the whole system. A little Bash loop that just tells the model to "look at this file" for every file is clearly not a "moat" of a system

danieltanfh952• 3 months ago

People really lack imagination. The point here is that a dedicated attacker with a good harness and really cheap models can run the attack regardless. It's like portscan/url search attacks. They could run all of these against all codebases and clients. However, on the flip side, this also means we could run cheap models against every PR made, and do a thorough red-team security review.

None of these requires mythos. If anything we just need Opus 4.5+ that is not lobotomised.

tptacek6• 3 months ago

That is a point. It might even be true. But showing a small model an example of vulnerable code and asking to confirm that it is vulnerable code isn't evidence for that point!

maevyn11• 3 months ago

Yea I think if you read the actual design of the test they are presenting as evidence it shows that what these small models are doing is not the same as what Mythos did. They isolated the vulnerable code down to the vulnerable subset of the function and provided hints in the prompt about all of the key contextual factors that matter to finding the vulnerability. That makes the problem significantly easier.

I realize they are trying to prove that an agentic harness running small models can ultimately achieve the same thing as what Mythos did, but they are handwaving away the steps it takes to construct the context Mythos handled in model and using a misleading test result to prove small models can handle the key step.

Poor evidence of a premise that logically wouldn't even be proven if the their evidence was valid. If they could find these types of vulnerabilities with the same effectiveness they would have done it already.

ehnto• 3 months ago

So it follows that the most efficient time to discover bugs is when you first write them.

mofeien2• 3 months ago

... or maybe when you see them triggered or exploited reproducibly, then the underlying bug will also be pretty easy to discover. But at that point, it's already too late. :)

I really like your original point, I never thought about it this way.

alanning• 3 months ago

Off-topic but is there an effort to test AI models against code versions with major historic bugs (Heartbleed, GHOST, log4j, etc)? Seems like the kind of thing that would be relevant in security-related AI benchmarks.

fred_is_fred• 3 months ago

If you cut out the vulnerable code from Heartbleed and just put it in front of a C programmer, they will immediately flag it. It's obvious.

Genuinely curious - why couldn't a static analyzer also find the issue then? Those have been worked on for 50+ years at this point, maybe longer.

herf• 3 months ago

There are a lot of details in the original article, in most cases comparing with Opus, which required "human guidance" to exploit the FreeBSD vulnerability:

https://red.anthropic.com/2026/mythos-preview/

Also "isolating the relevant code" in the repro is not a detail - Mythos seems to find issues much more independently.

robotswantdata• 3 months ago

They found a nail in a small bucket of sand, vs mythos with the entire beach reviewed.

ctoth2• 3 months ago

They recovered much of the same analysis

Really?

We isolated the vulnerable vc_rpc_gss_validate function, provided architectural context (that it handles network-parsed RPC credentials, that oa_length comes from the packet), and asked eight models to assess it for security vulnerabilities.

No.

lordofgibbons2• 3 months ago

Without showing false-positive rates this analysis is useless.

If your model says every line if your code has a bug, it will catch 100% of the bugs, but it's not useful at all. They tested false-positives with only a single bug...

I'm not defending anthropic and openai either. Their numbers are garbage too since they don't produce false-positive rates either.

Why is this "analysis" making the rounds?

davebren4• 3 months ago

It should at least get the same coverage anthropic got then, if not more.

sfink• 3 months ago

Yes, and in this case they pointed at the function, so a 1-bit model ("yes") would be correct. But it's not that bad. First, they included a test with a false positive. The small models got it right, Opus got it wrong. Second, they asked for an analysis. Look for "Exploitation reasoning, single follow-up prompt:" in the post. It's hard to tell how good they were at a glance, though apparently the full logs are available so you could pull them up.

Anyway, it seems like they erred in the up-front claim "small models found the vulnerability we pointed directly at!", but the findings are at least somewhat stronger if you read through the details.

The small models didn't match Mythos at exploitation. They suggested plausible exploits, but didn't actually try them out so I can't tell if they would have worked. Deepseek R1's sounds pretty convincing to me, but I'm not a good judge. (I'm more in the space of accidentally writing vulnerabilities, not seeking them out or exploiting them. Well, ok, I have a static analysis that finds some, at least.)

sealeck• 3 months ago

Why does the false positive rate matter if you have a verifiable oracle? You can just disregard anything that fails the oracle

lordofgibbons2• 3 months ago

What's the verifiable oracle in this scenario?

bhouston3• 3 months ago

This is quite misleading.

If you isolate the positive cases and then ask a tool to label them and it labels them all positive, doesn't prove anything. This is a one-sided test and it is really easy to write a tool that passes it -- just return always true!

You need to test your tool on both positive and negative cases and check if it is accurate on both.

If you don't, you could end up with hundreds or thousands of false positives when using this on real-world samples.

The real test is to use it to find new real bugs in the midst of a large code base.

grg0• 3 months ago

AKA F-score. https://en.wikipedia.org/wiki/F-score

operatingthetan• 3 months ago

My theory is that Mythos is basically just Opus with revised context window handling and more compute thrown at it. So while it will be a step forward, it is probably primarily hype.

appcustodian22• 3 months ago

N model is basically just N-1 model with revised context window handling and more compute thrown at it

pertymcpert3• 3 months ago

Shit. Really? You mean they modified their frontier model to improve it and make it better and just called it a day? That their benchmarks which show step change improvements are just the result of successive changes on an EXISTING MODEL?

Say it isn't so! I for one like to start from scratch each time I release my version of my compiler toolchain.

chjj• 3 months ago

They didn't call it a day. They created an entire deceptive hype cycle around it.

nickdothutton• 3 months ago

POC of GTFO should apply to AI models too, or the false positive rate will overwhelm.

vmg122• 3 months ago

The technique Anthropic uses was demonstrated by Nicholas Carlini in a talk he gave 2 weeks ago and it's very simple, when asking LLMs to review code, ask them to focus its review on one file in a single session. Here is the video with the timestamp (watch through to ~5:30, they show two different ways of prompting claude).

https://youtu.be/1sd26pWhfmg?t=204

https://youtu.be/1sd26pWhfmg?t=273

IMO the big "innovation" being shown by Mythos is the effectiveness with prompting LLMs to look for security vulnerabilities by focusing on specific files one at a time and automating this prompting with a simple script.

Prompting Mythos to focus on a single file per session is why I suspect it cost Anthropic $20k to find some of the bugs in these codebases. I know this same technique is effective with Opus 4.6 and GPT 5.4 because I've been using it on my own code. If you just ask the agent to review your pr with a low effort prompt they are not exhaustive, they will not actually read each changed file and look at how it interacts with the system as a whole. If the entire session is to review the changes for a single file, the llm will do much more work reviewing it.

Edit: I changed my phrasing, it's not about restricting its entire context to one file but focusing it on one file but still allowing it to look at how other files interact with it.

mirsadm• 3 months ago

How is that going to find anything that interacts across files?

vmg122• 3 months ago

My phrasing wasn't clear but you aren't telling it to only look at one specific file but to focus its review on one file. Updated my original comment.

appcustodian22• 3 months ago

I would think that it is still capable of exploring the codebase and reading other related files like any other coding agent already does.

nodja• 3 months ago

You misunderstood.

Instead of asking the model: "Here's this codebase, report any vulnerability." you ask. "Here's this codebase, report any vulnerability in module\main.c".

The model can still explore references and other files inside the codebase, but you start over a new context/session for each file in the codebase.

TacticalCoder2• 3 months ago

I don't dispute the fact that it's more than cool that we have a new tool to find security exploits (and do many other things) but... A big shoot-out to OpenBSD?

We're literally talking about the biggest computers on the planet ever, trained with the biggest amount of data ever available to a system, with the biggest investment ever made by man or close to it and...

The subtlest security bug it can find required: going 28 years in the past and find a...

Denial-of-service?

A freaking DoS? Not a remote root exploit. Not a local exploit.

Just a DoS? And it had to go into 28 years old code to find that?

So kudos, hats off, deep bow not to Mythos but to OpenBSD? Just a bit, no!?

mrifaki• 3 months ago

finding vulns in a large codebase is a search problem with a huge negative space and what aisle measured is classification accuracy on ground-truth positives, those are different tasks so a model that correctly labels a pre-isolated vulnerable function tells me almost nothing about that model's ability to surface the same function out of a million lines of unrelated code under a realistic triage budget

the experiment i'd want to see is running each of the small models as an unsupervised scanner across full freebsd then return the top-k suspicious functions per model and compute precision at recall levels that correspond to real analyst triage budgets, if mythos s findings show up in the small models top 100, i'd call that meaningful but if they only surface under 10k false positives then the cost advantage collapses because analyst triage time is more expensive than frontier model compute to begin with

second thing i keep coming back to is the $20k mythos number is a search budget not a model cost, small models at one hundredth the per-token price don't give us one hundredth the total budget when the search process is the same shape, i still run thousands of iterations and the issue for autonomous vuln research is how fast the reward signal converges and the aisle post doesn't touch any of this

cedws• 3 months ago

Didn’t they also use Mythos to scan Linux many times over and it only found one DoS bug or something? I find it hard to believe there is only one security bug lurking.

elzbardico• 3 months ago

I think that probably Mytho's mojo comes from a lot of post-training on this kind of task.

I occasionally pick up contract work doing coding annotation to make some quick extra money, and a few months ago one of the projects was heavily focused on spotting common memory access bugs in C and C++.

hedgehog• 3 months ago

It's strange to me they didn't reduce to PoC so the quantitative part is an apples-to-apples comparison. You don't need any fancy tooling, if you want to do this at home you can do something like below in whatever command line agent and model you like. A while back I did take one bug all the way through remediation just out of curiosity.

"""

Your task is to study the following directive, research coding agent prompting, research the directive's domain best practices, and finally draft a prompt in markdown format to be run in a loop until the directive is complete.

Concept: Iterative review -- study an issue, enumerate the findings, fix each of the findings, and then repeat, until review finds no issues.

Your job is to run a security bug factory that produces remediation packages as described below. Design and apply a methodology based on best practices in exploit development, lean manufacturing, threat modeling, and the scientific method. Use checklists, templates, and your own scripts to improve token efficiency and speed. Use existing tools where possible. Use existing research and bug findings for the target and similar codebases to guide your search. Study the target's development process to understand what kind of harness and tools you need for this work, and what will work in this development environment. A complete remediation package includes a readme documenting the problem and recommendations, runnable PoC with any necessary data files, and proposed patch.

Track your work in TODO.md (tasks identified as necessary) LOG.md (chronological list of tasks complete and lessons) and STATUS.md (concise summary of the current work being done). Never let these get more than a few minutes out of date. At each step ensure the repo file tree would make sense to the next engineer, and if not reorganize it. Apply iterative review before considering a task complete.

Your task is to run until the first complete remediation package is ready for user review.

Your target is <repo url>.

The prompt will be run as follows, design accordingly. Once the process starts, it is imperative not to interrupt the user until completion or until further progress is not possible. Keep output at each step to a concise summary suitable for a chat message.

``` while output=$(claude -p "$(cat prompt.md)"); do echo "$output"; echo "$output" | grep -q "XDONEDONEX" && break; done ```

</directive>

Draft the prompt into prompt.md, and apply iterative review with additional research steps to ensure will execute the directive as faithfully as possible.

"""

cmiles8• 3 months ago

Mythos is clearly a nice improvement. It’s also clear there’s a lot of unfounded hype around it to keep the AI hype cycle going.

Gating access is also a clever marketing move:

Option A: Release it but run out of capacity, everyone is annoyed and moves on. Drives focus back to smaller models.

Option B: A bunch of manufactured hype and putting up velvet ropes around it saying it’s “too dangerous” to let near mortals touch it. Press buys it hook, like, and sinker, sidesteps the capacity issues and keeps the hype train going a bit longer.

Seems quite clear we’re seeing “Option B” play out here.

throwaway13337• 3 months ago

So there are two competing narratives:

1. Mythos uniquely is able to find vulnerabilities that other LLMs cannot practically.

2. All LLMs could already do this but no one tried the way anthropic did.

The truth is one of these. And it comes down whether the comparison is apples to apples. Since we don't know the exact specifics of how either tests were performed, we lack a way of knowing absolutely.

So I guess, like so many things today, we can to pick the truth we find most comfortable personally.

goldenarm• 3 months ago

People have found 0days assisted by LLMs for a while, and none of them wrote hype pieces to find an excuse not to release their 10x bigger model in the middle of a GPU shortage.

https://sean.heelan.io/2025/05/22/how-i-used-o3-to-find-cve-...

bryantwolf2• 3 months ago

All of this discourse seems very bizarre.

If smaller models can find these things, that doesn’t mean mythos is worse than we thought. It means all models are more capable.

Also if pointing models at files and giving them hints is all it takes to make them find all kinds of stuff, well, we can also spray and pray that pretty well with llms can’t we.

It just points to us finding a lot more stuff with only a little bit more sophistication.

Hopefully the growing pains are short and defense wins

davebren4• 3 months ago

If smaller models can find these things, that doesn’t mean mythos is worse than we thought. It means all models are more capable.

It means "it's so dangerous we can't release it" was a blatant lie since anthropic would have already known this.

bryantwolf2• 3 months ago

Sure, I think it’s reasonable to tell Anthropic the barn door is already open.

Though, like, I guess I expect that when this comes out, all the opus traffics will move over. It does appear to be much more capable, just jury is out about how much more capable

pertymcpert3• 3 months ago

No one seems to have actually read the system card all the way through.

The reason they didn't publish it was that it's orders of magnitude more successful at writing exploits vs Opus 4.6, which only managed it something like 2% of the time.

abel_• 3 months ago

This misses the broader ongoing trend. For a few million dollars, of course you can create a startup that builds tools it can use to more efficiently find code vulnerabilities. And of course you can do this with weaker models with scaffolds that incorporate lots of human understanding. The difference now is that you don't need an expensive team, nor a bunch of human heuristics, nor a million dollars. The requisite cost and skill are falling rapidly.

yalogin• 3 months ago

Intuitively every existing model has already been trained on all code, all vulnerabilities reported, all security papers. So they all have the capability. Small models fall short because they may not be able to find a vulnerability that spans across a large function chain but for the most part they should suffice too.

Of course I say this without any knowledge of what mythos is doing or how it’s different. I am sure it’s somehow different

nomel• 3 months ago

Not intuitive at all. Not all models are equally capable, just because they had the same training data. The model architecture (as a whole) is very important. To reduce capability, you can reduce layers, tool use, thinking, quantize it, etc. This is trivially proven by a cursory glance in the rough direction of any set of benchmarks (or actual use).

Using small models as a classifier "there might be a vulnerability here" is probably reasonable, if you have a model capable of proving it. There are many companies attempting this without the verification step, resulting in AI vulnerability checker being banned left and right, from the nonsense noise.

omcnoe2• 3 months ago

The methodology here is completely wrong, outright dishonest.

Finding a needle in a haystack is easy if someone hands you the small handful of hay containing the needle up front, and raises their eyebrows at you saying “there might be a needle in this clump of hay”.

chopete3• 3 months ago

The impact of the Mythos announcement on the cybersecurity firms( like Crowdstrike,ZScalar etc) is big enough(10-15% drop in stock price) and this pushback is expected.

Companies like Aisle.com (the blog) and other VAPT companies charge huge amounts to detect vulnerabilities.

If Cloud Mythos become a simple github hook their value will get reduced.

That is a disruption.

zer00eyz• 3 months ago

Crowdstrike, no pe because it just had its first profitable quarter (38 million)

ZScalar No PE

Palo Alto Networks Inc (PANW) 86 PE

Fortinet : (FTNT) 31.63 PE

That last one, didn't get hit at all by the Mythos announcement, because at some level it has at least some grounding in fiscal reality.

throwa3562622• 3 months ago

If anyone can get Crowdstrike to go bankrupt I will be rooting for them.

Those guys are the reason our new work laptops run at 1/3 of speed.

While back crowdstrike managed to simultaneously crash every windows computer and bring every major company to a halt and somehow are still around.

coppsilgold• 3 months ago

LLMs are wordsmith oracles. A lot of effort went into trying to coax interactive intelligence from them but the truth is that you could have probably always harnessed the base models directly to do very useful things. The instruct tuned models give your harness even more degrees of freedom.

A while ago, the autoresearch[1] harness went viral, yet it's but a highly simplified version of AlphaEvolve[2][3][4].

In the cybersecury context, you can envision a clever harness that probes every function in a codebase for vulnerabilities, then bubbles the candidates up to their callsites (and probes whether the vulnerability can be triggered from there) and then all the way to an interface (such as a syscall) where a potential exploit can be manifested. And those would be the low hanging fruit, other vulnerabilities may require the interplay of multiple functions. Or race conditions.

[1] <https://github.com/karpathy/autoresearch>

[2] <https://deepmind.google/blog/alphaevolve-a-gemini-powered-co...>

[3] <https://arxiv.org/abs/2506.13131>

[4] <https://github.com/algorithmicsuperintelligence/openevolve>

AlexandrB• 3 months ago

The whole "this tool is too dangerous to be public" idea reeks of marketing. Just like all the "AI is an existential threat" talk a year ago. These companies are using ideas usually reserved for something like nuclear weapons to make their products look more impressive.

npilk• 3 months ago

Wouldn't this mean we're even more cooked? I've seen this page cited a few times as evidence that Mythos is no big deal, but if true then the same big deal is already out there with other models today.

davebren4• 3 months ago

As cooked as we were pre-LLMs knowing that security exploits are relatively easy to learn about online and use, yet things keep chugging along.

dominicq• 3 months ago

This would just speed up the discovery -> patch cycle, at least until such time that all the low hanging fruit (=represented in training data) is patched.

Though another possibility would be that since LLMs generate so much code, the LLM vulnerability discovery would just keep chugging along and we'd simply settle for the same amount of potential vulns, same relative vulnerability-exploit-patch dynamics, though higher in absolute numbers.

slibhb2• 3 months ago

The best way to think of Anthropic's communication about Mythos is as advertisement. It's basically "our model is too smart to release" which suggests they're ahead of OpenAI (without proof)

pardon_me• 3 months ago

The whole company is like that. If things were as amazing as advertised, they wouldn't even need to advertise. Or to release models to the public at all.

boelboel• 3 months ago

Seen similar things with Openai and Palantir.

slibhb2• 3 months ago

Yes. OpenAI does the exact same thing.

charcircuit• 3 months ago

The thesis that the system is more important than the model is not bitter lesson pilled. I would not bet on this in the long term. We will get to the point where you can just tell the model to go find and classify the severity of all security problems with a codebase.

midnitewarrior• 3 months ago

At the center of every security situation is the question, "is the effort worth the reward?"

We prepare security measures based on the perceived effort a bad actor would need to defeat that method, along with considering the harm of the measure being defeated. We don't build Fort Knox for candy bars, it was built for gold bars.

These model advances change the equation. The effort and cost to defeat a measure goes down by an order of magnitude or more.

Things nobody would have considered to reasonably attempt are becoming possible. However. We have 2000-2020s security measures in place that will not survive the AI models of 2026+. The investment to resecure things will be massive, and won't come soon enough.

_pdp_• 3 months ago

  find ./ \( -name '*.c' -o -name '*.cpp' \) -exec agent.sh -p "can you spot any vulnerabilities in {}" \;

abhinaystha• 3 months ago

Tech companies are just hyping their model to that the bubble wont burst so easily.

nfcampos• 3 months ago

Anthropic marketing (and even supposedly technical write ups) sadly has become more hyperbole and less substance over time imo. This technology is so impressive on its own, really feels like shootings themselves in the foot in the long run, but what do I know

Case in point here where they conveniently fail to report the false positive rate, while also saying that if it wasn’t for Address Sanitizer discarding all the false positives this system would have been next to useless

decidu0us90343• 3 months ago

Right now, we accept false positives as long as you can sort them out. I think it's pretty typical that >99% of fuzzer runs don't result in new coverage. Of course they're far from useless without feedback but it's better to have it if you can. I guess the question is does the llm approach have lower costs for validation and triaging vs just fuzzing alone, unclear to me. Anthropic would like people to believe automation is this scary new unknown

palashdeb• 3 months ago

Been tracking this since the blog post, quick a big deal they are making it.

thywis• 3 months ago

Sure, but it's more about whether the small model can find the vulnerability that bigger model can.

mrinterweb• 3 months ago

I feel like there have been enough hyperbolic claims by Anthropic, that I'm starting to get some real Boy Who Cried Wolf energy. I'm starting to tune out, and assume it is a marketing ploy. Trust me, I'm an Antropic fan, and I pay my $200/month for max, but the claims are wearing thin.

starboyy• 3 months ago

Tagline is very funny

oliveiracwb• 3 months ago

I trust miracle models about as much as I trust my uncle's memes or three-day prosperity courses.

etothet• 3 months ago

My big question around the Mythos FUD, is this: if we take for fact the Mythos is as powerful and dangerous as we’re being told (and I realize this is part marketing), and because of that Anthropic isn’t going to release it…how long can that last? Isn’t it reasonable that OpenAI or xAI or some other company - or foreign government - will come up with a similarly dangerous model fairly soon?

So what’s Anthropic’s plan here? How long can they withhold releasing Mythos or something Mythos-like? Is it reasonable to think they - or another AI provider - are going to dumb down future models so they’re less dangerous? I personally don’t think that’s the case.

I’m not saying Anthropic should or shouldn’t release Mythos, but it leaves me wonderingwhat’s going to be different in, say, 6 months or even a year when they or another provider releases a model as dangerous as we’re being told Mythos is?

dev1ycan• 3 months ago

It was obvious since the start that 1)it's probably all javascript based or android websites/programs that contain a ton of "vulnerable" libraries (or really old closed sourced c++ code).

Also you're not helping your case as a software company if you feed your code to an LLM, great job making it all public, because it will most likely be used as training data like it or not.

Animats• 3 months ago

What are they finding? Buffer overflows? Something else?

Also, if someone has the time and tokens, would they please run the OpenJPEG 2000 decoder through this tester? It's known to be brittle. The data format has lots of offsets, and it's permitted to truncate the file to get a lower-rez version. That combo leads to trouble.

ares623• 3 months ago

Once again, it would've been so easy and simple to remove all doubt from their claims: release all the tools and harnesses they used to do it and allow 3rd parties to try and replicate their results using different models. If Mythos itself is as big a moat as they claim it is, then there shouldn't be any problem here.

They did the same stunt with the C compiler. They could've released a tool to let others replicate it, but they didn't.

StrauXX• 3 months ago

A lot of comments here are dismissing this post because the relevant code was isolated. But thats the exact same thing Anthropic did with Mythos! They describe their (very lean) harness in the Anthropic Red Mythos blog post. The harness first assigns each file in the given codebase an importance value. Then points claude code at the cpdebase with a prompt stating that it should focus on that file. It spawns a claude code instances for each file in the codebase.

So no, the fact that the posters isolated the relevant code does not invalidate their findings.

[1] https://red.anthropic.com/2026/mythos-preview/

make_it_sure2• 3 months ago

check other comments, they didn't

felipeerias2• 3 months ago

From the article:

Our tests gave models the vulnerable function directly, often with contextual hints (e.g., "consider wraparound behavior").

grandinquistor• 3 months ago

I mean you can still scale that? Ask a lighter model to go through every function to find vulnerabilities, take output to bigger model like Opus and classify the critical ones.

jeffrwells• 3 months ago

Anthropic has become a PR vaporware company

pugazh35• 3 months ago

Maybe P vs NP, plays a silent role in it

tonymet• 3 months ago

My router had a broken IPv6 firewall and lacked root access. I needed a root shell to run ip6tables. I exfil'd the code and ran Gemini to discover shell injection vulnerabilities. I was able to get root shell to run ip6tables and add the firewall. I had notified the vendor for a couple years that the firewall was broken and showed them the issue but it hadn't been fixed.

make_it_sure2• 3 months ago

The only reason that's on top of HN is that people really want Mythos to be bad. This "study" is a cheap gimmick, they pointed to the actual location with the vulnerability and said "something is bad here, find it".

The hardest part is locating the issue, if you point directly to it, you're not comparing the same thing by far, and they know it. This was just a stunt by them to get publicity, they knew what they were doing and many fell for it, including here.

stringfood• 3 months ago

Case in point: I found the same OpenBSD bug once I knew where it was and I am highly uneducated

onesociety2022• 3 months ago

This article is written by a company building an AI cybersecurity solution. Not sure how much you can trust them on this topic - their business will get destroyed if Mythos is actually so superior to existing models that it doesn’t require a big investment into the scaffold/harness to find security vulnerabilities. If the model is too good, then what’s the value of their solution?

muyuu2• 3 months ago

I think the "Mythos" name is genius. The people at Anthropic make a bunch of claims and the public is expected to just believe them without any possibility of testing those claims or reproducing those results, and since so many people are invested in this saviour for the Global economy, or in the industry in general, or in hype to feed their engagement-based income sources, then there is faith to spare.

Meanwhile this mythical beast wasn't able to prevent the Bun vulnerability that exposed their code, let alone precluding the need to acquire that IP in the first place for presumably hundreds of millions of $$$, instead of coding a better replacement or a solution of its own.

What is real and measurable is that subscription plan users are getting a much degraded service for the same money through both open and hidden policies, while Anthropic moves compute to serve off-the-counter customers. The same people who come with the most obvious and brazen lies to dismiss the clear degradation of their service also come with this "security" justification for a move that looks just like good old market segmentation which would perfectly fit the strong symptoms that they cannot afford to offer tokens at a competitive price in this market.

tokioyoyo• 3 months ago

There are two possibilities:

a) Anthropic is lying, and every company that is collaborating on vulnerability squishing project is an accomplice in this big lie b) Anthropic has then goldest gold of the shovels to sell to people, which is actually useful for enterprises

Everyone, including Ant, understands that other companies will catch up in terms of model strength. So it’s a damned if you do, damned if you don’t position wrt releasing it to the public.

phire• 3 months ago

The model is probably legitimately better. But it might not be enough better to justify the extra cost of inference.

They know if they released it publicly, people will be able to see exactly how smart it is, and adjust their demand correspondingly. Anthropic will either need to price it high enough that nobody uses it (and the hardware is sitting mostly idle to servicing a few customers), or lower their profit margins (potentially below cost) to price it fairly.

So instead, they bundle it with this fancy new exploit finding scaffold, and sell the combined it to enterprise customers. I bet the scaffold works fine with smaller models, but gets notably improved results with Mythos.

The two products support each-other, and with the exclusive bundle Anthropic can get more profit selling both together than they would get selling them individually.

And as an added bonus, people over estimate the capability of this unreleased model, providing hype for Anthropic.

JSR_FDED• 3 months ago

One very clever consequence of Anthropic's guarded release of the Mythos model is that they've kind of claimed the position of best in class here, and also positioned themselves as the responsible vendor in this space in one fell swoop.

muyuu2• 3 months ago

OpenAI pulled the same trick with GPT3. It's amazing how well it's working judging by the comments I'm hearing from people I know exist. Because out there on social media, who knows.

kilroy123• 3 months ago

Well said. I really hope the Chinese models keep getting better. Competition is good.

nickpsecurity• 3 months ago

We've always had good tools for program analysis and testing. They're usually exhorbitantly expensive.

I'm hoping the good results with AI models drive down the prices of traditional tools. Then, we can train open models to integrate with them.

morpheuskafka• 3 months ago

Everyone is commenting that this doesn't count because they pointed it at the specific files that Mythos already found vulnerable.

But sometimes you do know where vulnerabilities are and still don't know what they are. For example, an update may be released in beta changing the part of the Mac or Windows kernel or some app, but they haven't published the CVE yet. If locally runnable (even with significant compute costs) LLMs can find and exploit it based on either the location of the changed file or the actual diff of the compiled output, we could see exploits before the update ever went to production?

jurschreuder• 3 months ago

All these models will completely mess up your code if you let them.

And if they constantly scan your code with various settings and updates you will spend hours a day reading, trying to understand locally coherent but structurally incoherent vibes trying to pinpoint the exact reasoning flaw. Exhausting.

Loeffelmann• 3 months ago

locally coherent but structurally incoherent

Perfectly summarizes what I hate about AI code. The diff looks fine but if you take a step back its an absolute mess. I mean have you looked at the Claude Code or Openclaw codebases? that is the result of full on vibecoded. A bloated unattainable mess that no one understands.

rurban• 3 months ago

If they would have watched Carlini's "unblocked" talk on youtube, which is much more detailed than the blog post, they would not need this writeup. He was worried about the reproducers of the zero-day's. Not the actual zero-days that much.

solatic• 3 months ago

Most commenters here: "Mythos is powerful because you can point it at a whole codebase, if you point the smaller models at a whole codebase and iterate through small sections of code, you'll get too many false-positives to handle."

This misses the point entirely. You pay $20k as a one-time fee to establish a baseline. Your codebase develops one PR at a time, which... updates isolated sections of code. Which means you don't need Mythos for a PR, just small, open-weight models. Maybe you run Mythos once a year to ensure that you keep your baseline updated and reduce the risk that the open-weights models missed anything.

Seeing this as anything but a huge win for open-weights models and a huge loss for Anthropic misses the point entirely. Mythos isn't something you can persuade Fortune 500 companies to spend $20k/day or even $20k/week to spend on, like they were hoping for. $20k/year is a lot less valuable, and it won't justify development costs or Anthropic's growth multiple.

bottlepalm• 3 months ago

None of these comments will age well. I don't know if it is denial, or cope, or being threatened by AI or what, but no one is taking AI serious enough. Simply take what is being presented at face value, stop thinking everything is a conspiracy and realize the implications. Zero days in software are one thing, it's a hop skip and jump from there to zero days in biology - and no one will be laughing about that.

latentframe• 3 months ago

Good writeup seems like it’s not really the big model against the small one anymore and if smaller models can do most of the job once the context is smaller then it’s more about the system around them and the expertise ...

brador• 3 months ago

I want that Doom thing but finding vulnerabilities using AI models.

Like I discovered a JavaScript vulnerability using a fridge.

high_byte• 3 months ago

"The correct answer: not currently vulnerable, but the code is fragile and one refactor away from being exploitable."

absolutely. I see this pattern all the time when doing security audits - code that is nearly-vulnerable. I would mark these things as informational and recommend to harden them anyway, and any model would do a good job to do the same.

JoshTko• 3 months ago

I bet Anthropic just had marketing strategy discussions with Mythos to get the "breakthrough hacking tool!" framing.

ptrwis• 3 months ago

When you pair-programming with AI, even Haiku is very good. Just treat is as you assistant.

tom-blk• 3 months ago

Interesting comparison, cool article!

HarHarVeryFunny• 3 months ago

Most of the comments here seems to be responding to the issue of finding vulnerabilities, rather than exploiting them, but the Anthropic claim is that the Mythos advance is being able to actually develop exploits whereas Opus 4.6 had been able to find vulnerabilities, but was poor at being able to develop exploits for them.

It's also noteworthy that Anthropic attributes Mythos' improvement to advances in "coding, reasoning and autonomy", and that the autonomy part seems especially important since they go on to say that trying to develop exploits included adding debug code to projects, running them under a debugger, etc.

When comparing the capabilities of Mythos to previous generation and/or smaller models, it seems it would therefore be useful to distinguish between identifying potential vulnerabilities and actually trying to build exploits for them in agentic fashion. Finding the "needle in a haystack" (potential vulnerability) is one aspect, but the other part is an agentic exploit-writing harness being handed the needle and asked to try to exploit it.

I wonder how much effort Anthropic put into building the harnesses and environments for Mythos to run, modify and debug code? For example, was Mythos set up to be able to build and run a modified BSD in some virtual environment, or did it just take suspect functions and test those in isolation?

It'd be interesting to put the capabilities of Opus 4.6, Mythos, and other models into perspective by comparing them to traditional non-AI static analysis security scanning tools. Anthropic mention that the open source projects they scanned came from the OSS-Fuzz corpus, but as far as I can see they don't say what other tools have, or have not, been used to scan these projects.

It'd also be interesting to know to what extent Mythos was explicitly RL trained to develop exploits (especially since it sounds as if Anthropic have the dataset and environment needed to do this) as opposed to this just being a natural consequence of the model being better. If this was the case then it might be a large part of why they are not releasing it - can't really position yourself as strong on security if you deliberately develop and release a hacking tool!

ehtbanton• 3 months ago

Wake me up when Anthropic does something right again...

krschacht• 3 months ago

At the end of this article it states, "Our tests gave models the vulnerable function directly, often with contextual hints (e.g., "consider wraparound behavior"). A real autonomous discovery pipeline starts from a full codebase with no hints." I'm not a cybersecurity expert, but isn't 80% of the challenge finding where the exploit lives in the code!?

That really undermines the author's claims. This article feels dishonest in it's claim that "small, cheap, open-weights models ... recovered much of the same analysis."

hamuraijack• 3 months ago

This feels so dishonest. If the vulnerabilities are a needle in the haystack. Mythos was just given the haystack and told to find the needle while the authors pointed to a spot in the haystack and told their LLM to try looking around there. That's not even close to being the same.

sheepscreek• 3 months ago

I think what made Mythos a big deal is not that it could find vulnerabilities. Opus can do that too. But Mythos went a step further and autonomously built exploits very successfully whereas Opus struggled to do that.

Most modern day exploits are multi-step requiring a multitude of skills to pull off successfully.

flafferay• 3 months ago

This to me has sounded like a huge PR stunt from the start. “Too dangerous” was honestly the first headline I read when I first heard about Mythos.

Small models also found the vulnerabilities that Mythos found

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