Reverse Engineering US Airline's PNR System and Accessing All Reservations

https://alexschapiro.com/security/vulnerability/2025/11/20/avelo-airline-reservation-api-vulnerability

by bearsyankees • 7 months ago

134 60 7 months ago

mattmaroon3• 7 months ago

Major? Avelo?

s1mon• 7 months ago

Agreed. I read the headline as "... US Airlines' ..." not "... US Airline's ..." and it seemed much more concerning. Instead it's a single airline I've never heard of. Looking them up, they are more established than I might have guessed (started as Casino Express Airlines 38 years ago, but current incarnation is only 4 years old), but also pretty small - roughly 1/100 the staff and 1/50 the fleet of United.

https://en.wikipedia.org/wiki/Avelo_Airlines

mattmaroon3• 7 months ago

Ha I guess I flew them in a past incarnation but didn’t know that.

Nextgrid3• 7 months ago

This is about a non-rate-limited endpoint providing ticket data given a booking code only (and not last name as it's usually the case), which makes it feasible to bruteforce the entire search space.

(unfortunately, I feel like AI was overused in authoring the writeup)

dado3212• 7 months ago

What makes you say that? This didn't read like AI slop to me.

delfinom• 7 months ago

There's an emdash, no human being uses emdashes.

Nextgrid3• 7 months ago

Overuse of bulleted lists, unnecessary sensationalism, sentences like "The requests flew. There was no WAF, no IP blocking, no CAPTCHA." and so on. It reeks of someone pasting some notes into a chat prompt and asking it to spruce it up for publication.

PKop3• 7 months ago

Pattern recognition skill issue then. It did to me.

"The fallout"

This flaw was critical.

And other vibes. You know it when you see it, though it may be hard to define.

tverbeure• 7 months ago

This incident is a stark reminder

A stark reminder is a stark reminder about the existence of AI slop. You see the phrase a lot in social media comment spam.

filearts• 7 months ago

Is it really AI slop if someone leverages AI to improve / transform their novel experiences and ideas into a rendition that they prefer?

I'm not suggesting whether or not the article is AI assisted. I'm wondering if the ease of calling someone's work "AI slop" is a step along the slippery slope towards trivializing this sort of drive-by hostility that can be toxic in a community.

Nextgrid3• 7 months ago

You are right about the toxicity, I will edit my comment.

There's a difference between leveraging AI to proofread or improve parts of their writing and this - I feel like AI was overused here; gave the whole article that distinctive smell and significantly reduced its information density.

klysm• 7 months ago

Annoying sensationalist writing, but good find!

CtrlAltNerd• 7 months ago

Great work, very impressive find.

mtlynch2• 7 months ago

The Avelo team was responsive, professional, and took the findings seriously throughout the disclosure process. They acknowledged the severity, worked quickly to remediate the issues, and maintained clear communication. This is a model example of how organizations should handle security disclosures.

Sounds like no bug bounty?

It's great if OP is happy with the outcome, but it's so infuriating that companies are allowed to leak everyone's data with zero accountability and rely on the kindness of security researchers to do free work to notify them.

I wish there was a law that assigned a dollar value to different types of PII leaks and fined the organization that amount with some percentage going to the whistleblower. So a security researcher could approach a vendor and say, "Hi! I discovered vulnerabilities in your system that would result in a $500k fine for you. For $400k, I'll disclose it to you privately, or you can turn me down and I'll receive $250k from your fines."

edent• 7 months ago

I wish there was a law that assigned a dollar value to different types of PII leaks

There is. It is called GDPR.

Plenty of companies have been fined for leaks like this.

Some countries also have whistleblower bounties but, as you might expect, there are some perverse incentives there.

mtlynch2• 7 months ago

Yeah, as an American, I'm jealous of many aspects of GDPR. I really appreciate you blogging / tooting about experiences protecting your rights under GDPR. I wish we had 1/10th of the consumer privacy protections you have.

How does security research like this work out in practice, in the EU?

I read a lot of vulnerability writeups like this and don't recall seeing any where the author is European and gets a better outcome. Are security researchers actually compensated for this type of work in the EU?

billy99k• 7 months ago

The GPDR makes it so small companies need to hire expensive lawyers to be compliant (and you still don't know for sure, based on the laws)

How about fining individual developers with poor coding practices?

advisedwang• 7 months ago

The GDPR (in art 32) only requires that "the controller and the processor shall implement appropriate technical and organisational measures to ensure a level of security appropriate to the risk". I expect it's quite common for a company to get hacked even if they meet that level. I think the parent comment was imagining that any leak is automatically fined, regardless of whether the company had met some security requirement.

samuria• 7 months ago

Does GDPR mandate a payout to the researcher after disclosure?

bossyTeacher• 7 months ago

it's so infuriating that companies are allowed to leak everyone's data with zero accountability and rely on the kindness of security researchers to do free work to notify them.

This is a matter for lawmakers and law enforcement. Campaign for it. Nothing will change otherwise

jbergler• 7 months ago

The 6 hour claim is interesting, but I highly doubt Avelo (or any airline) would handle 100k requests/sec

If we consider that the real major's move about 400k-500k passengers/day, let's be really optimistic and say that they check their booking 6 times a day for the week before they fly. That's around 250 requests/sec.

Anyone know about the consumer facing tech stacks at airlines these days? Seems unlikely that they'd have databases that would auto scale 400x...

kiklion• 7 months ago

I doubt their API would handle 100k requests per second. That math was roughly indictive of what the cost to send 100k requests per second would look like. He did mention that that was assuming the target didn't have rate limiting, either intentional or just pure limits of the hardware.

bronco21016• 7 months ago

Cloud API gateway providers advertise ~10,000 rps.

I think more likely the API would be behind some kind of bot protection that would shut this down before any kind of technical rate limit is reached.

commandlinefan• 7 months ago

They were responsive, professional, and took the findings seriously, patching the issues promptly.

The "issue" is that they're returning the entire PNR dataset to the front-end in the first place. He doesn't detail how they fixed it, but there's no reason in the world that this entire dataset should be dumped into Javascript. I got into pretty heated arguments with folks about this at Travelocity and this shit is exactly why I was so adamant.

didgetmaster• 7 months ago

The lack of needing the last name might have allowed a hacker to brute force the whole list; but it seems that even with a last name, it could expose a lot of PII. Just pass codes along with popular last names (Smith, Jones, Nelson, etc.) and it seems like it could spit out a bunch of reservations.

miki1232112• 7 months ago

I'd go for wang, Li and Zhang instead, maybe also Patel and Nguyen. Asian countries have a much more skewed surname distribution.

morpheuskafka• 7 months ago

Yes, it's also an issue when someone posts their bag tag/boarding pass/booking email online.

But that's the "industry standard" for checking a reservation online. Requiring airline login doesn't work because of tickets issued by travel agents or other airlines.

codethief• 7 months ago

Exactly, I came here to say this!

This two-factor system is generally secure. The space of all 6-character alphanumeric confirmation codes combined with all possible last names is astronomically large, making it impossible to “guess” a valid pair.

Depending on the threat model, the attacker's goal might not be to guess a single pair but to access any valid pair (of a booking with a flight date in the future, or maybe even in the past). Suddenly you're looking at thousands of valid booking codes and the attacker can try a couple dozen of common names. Brute-forcing valid pairs then becomes relatively easy.

miki1232112• 7 months ago

Do we know what GDS Avelo is using? In other GDSes, is the confirmation code always sufficient to fully identify a booking? I was under the impression that PRLs could be re-used as long as the passenger surname was different.

The space of all possible PRLs is about 2 billion, I can imagine a really big Airline moving that many passengers.

rootsudo• 7 months ago

They use a service of Sabre but not Sabre GDS. it’s called Radixx.

Yes in other GDS, it can be enough to identify a full booking. That’s why airlines prefer ticket or coupon number since the first two digits are the airline ticket stock / identifier and then fare codes, etc

The requiring last name, and more info is more or less security since any pss system can query the airline first for that combination before requiring more info to return a match.

lxgr• 7 months ago

6 alphanumeric, case insensitive characters only allow for about 2 billion unique combinations. I’d have guessed there were more reservations made than that?

Or are PNR locators recycled after a while?

aardvark179• 7 months ago

Confirmation codes are not sufficient on their own, they cycle through them relatively quickly so they have to be combined with things like the passengers family name to actually identify the booking.

dboreham2• 7 months ago

Always consider rate limiting if you deploy a public endpoint. Always require authentication to perform resource-consuming and/or privacy leaking requests. (Requiring authentication makes rate limiting more practical since even a distributed attacker would need many credentials, which they probably don't have).

cake• 7 months ago

Any tips on how to define the rate limits for a web app with moderate traffic? For logged and anonymous users?

ISL4• 7 months ago

Avelo assists ICE daily with deporting people from the United States:

https://bsky.app/profile/jjindc.bsky.social/search?q=avelo

mattmaroon3• 7 months ago

Can’t load that but don’t they all? I can’t imagine any airline telling the federal government no.

apical_dendrite• 7 months ago

I think Avelo is the only airline that participates. The rest are charter companies.

ISL4• 7 months ago

It is likely that many airlines accommodate people who are being deported as regular passengers on outbound international flights.

For movement of humans at industrial scale, though, there are only a few operators with ICE contracts. Avelo, GlobalX, Eastern, Key Lime Air, and Omni come immediately to mind. For international flights, there's at least one Learjet operator that flies a bunch for them, too.

These days, the aforementioned carriers fly 20-30 flights/day. Here are Saturday's flights (apologies for the sign-in wall, but lalabote keeps their account somewhat locked down): https://bsky.app/profile/lalabote.bsky.social/post/3mai6lach...

Scoundreller• 7 months ago

Search is currently unavailable when logged out

Can you hook us up with some deep links?

ISL4• 7 months ago

Whoops -- was away from HN for a few days.

Here is JJ's account -- he is a prolific flight-tracker: https://bsky.app/profile/jjindc.bsky.social

Here is an Avelo flight moving through California right now: https://bsky.app/profile/jjindc.bsky.social/post/3malkyew432...

Here is an Avelo flight on the ground in Seattle on Saturday: https://bsky.app/profile/jjindc.bsky.social/post/3magxcnri32...

Avelo flies a number of flights each week for ICE.

RealSoyboyRoy• 7 months ago

I immediately disclosed this to the Avelo team. They were responsive, professional, and took the findings seriously, patching the issues promptly.

(emphasis my own)

Sorry but I strongly disagree with this phrasing. This is a company "serving over 6 million customers since its 2021 launch" (from Google) that took four weeks to patch an embarrassing security flaw, after being handed all the details on a silver platter.

Imagine a food chain serving a million meals a year was revealed to be storing their food products in unsanitary conditions, and it took them a full month to correct this. That story would make national headlines, not to mention they could get promptly shut down by any competent health ministry.

I think this attitude mostly reveals how complacent we've become about these """incidents""": we just expect this to happen, everywhere and all the time, then we just shrug and say "they fixed it within a month, how responsible of them".

Reverse Engineering US Airline's PNR System and Accessing All Reservations

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