Not all browsers perform revocation checking

https://revoked-isrgrootx1.letsencrypt.org/

106 82 10 months ago

revoked-isrgrootx1.letsencrypt.org

Dylan168074• 10 months ago

"Not all" is quite an understatement.

Titan2189• 10 months ago

I'm on Windows 11 (25H2 / 26220), and with Chrome (140), Edge (141) and Firefox (142) I wasn't able to find a browser that would show this as revoked.

zephyreon6• 10 months ago

Safari on iOS 26 certainly doesn’t show this page as revoked.

zephyreon6• 10 months ago

fwiw iOS happily displays the cert as very valid

https://f000.backblazeb2.com/file/0011public/Photo-2025-09-1...

mholt6• 10 months ago

That's because Apple uses their own CRLs, pretty much exclusively.

gslin• 10 months ago

https://crt.sh/?id=20924740030

sam_lowry_• 10 months ago

cyberax• 10 months ago

How do you even _get_ it to show as revoked? I tried FF, Chrome, Safari, curl, wget.

suriya-ganesh• 10 months ago

So far, I've tried this in, chrome, firefox, safari, arc and comet. loads in all of them

oofbey• 10 months ago

Sounds like letsencrypt is being quite premature by turning off OCSP. https://letsencrypt.org/2025/08/06/ocsp-service-has-reached-...

Might be EOL in some theoretical sense, but by turning it off they're ignoring reality. I know some organizations think this is the way to push standards forward. But to me it seems pretty irresponsible.

jsiepkes2• 10 months ago

As far as I know OCSP isn't enabled by default in any browser.

usr11063• 10 months ago

Do all other major CAs offer OCSP? Are all major browsers performing the check? I vaguely remember Firefox doesn't. Not at my desk now to check it...

Edit: I believe OCSP is tried, but silently ignored if there is no reponse quickly enough.

mholt6• 10 months ago

Sounds like letsencrypt is being quite premature by turning off OCSP.

Not really, since they now offer six-day certs, which makes revocation effectively irrelevant: https://letsencrypt.org/docs/profiles/#shortlived

dadrian2• 10 months ago

Yes, because this is not a security-relevant revocation.

wongogue• 10 months ago

It’s a negative on Firefox 142, Chrome 140 and iOS Safari.

8cvor6j844qw_d6• 10 months ago

Given the mentions of Chrome, Safari, Firefox, and the usual.

I would say "majority" rather than "not all" browsers perform revocation checking.

[1] https://gs.statcounter.com/browser-market-share

zephyreon6• 10 months ago

Seems rather problematic that a cert that appears to have been revoked 5 days ago isn’t recognized as revoked by virtually any browser. Is this an OCSP-related issue or do browsers actually do a bad job at checking for revocation?

Dylan168074• 10 months ago

If you don't do a job at all, have you done a bad job?

redleader553• 10 months ago

Checking for revocation doesn't scale and has serious privacy implications. There are two ways to do revocation: CRL and OCSP. CRL is a list that becomes huge over time - hosting it would require massive amounts of bandwidth and clients would need to download a lot of extra data. OSCP is more like a query API - did this cert expire? The problem is you need to make that query for each visit and you leak your IP address when you do that query. The hoster would need to provide capacity to run those queries and serve the result. For each visit you'd need to pay a few round-trips worth of delay before showing the content, sometimes while part of the content is downloaded: you download example.com, which has some CSS which is hosted at static.example.com, and the website redirects you to m.example.com which is the mobile version after running some JavaScript which detects the browser capabilities.

zephyreon6• 10 months ago

So the answer then is just much shorter-lived certs? I could definitely still see the need for an immediate revocation to be recognized near-instantaneously. Or in practice is that ultimately not necessary?

sugarpimpdorsey3• 10 months ago

CRL is a list that becomes huge over time - hosting it would require massive amounts of bandwidth and clients would need to download a lot of extra data.

Compared to what? 12MB JavaScript bundles and autoplay videos? Do CDNs still exist?

There's a finite number of CAs and browsers can be expected to perform caching. Delta CRLs also exist and the CAs can decline to include expired leaf certs.

This sounds like a made up problem that was solved 25 years ago.

tjoff2• 10 months ago

You could of course cache the list, only download whatever was new from a specific date. Short-lived certs would vastly reduce the list as well.

Not really sure how big of a problem a list could be?

goalieca• 10 months ago

CRL is a list that becomes huge over time

IETF will be gradually reducing maximum length of public certs to 47 days. I expect this will help some of the issue since expired certs can be removed from the list.

Ayesh5• 10 months ago

I was a big fan of OCSP-stapling and must-staple. Both of which are slowly being discouraged; LetsEncrypt refuses to issue must-staple certificates since a few months ago, and I think they are shutting down OCSP servers, if not shut down already.

The idea with OCSP-stapling is that the webserver fetches the OCSP data, caches it for TTL ~24 hours, and staples it to the HTTPS handshake. That way, the browser does not need to query the issuer's OCSP servers, avoiding both performance and privacy concerns. Revoked certificates will continue to work for up to 24 hours, but that, IMO, is within an accepted range compared to CRL that can take a lot longer.

The downside is that the HTTPS handshakes now contain a bit more data, and we want to keep this as minimal as possible.

yegle2• 10 months ago

I wonder if any free certificate issuers still support Must-Staple?

thayne4• 10 months ago

I don't think any browsers still support OCSP.

The problem with OCSP stapling is that it either the client has to fall back to doing OCSP checking itself if the server doesn't staple the signature, which has its own problems[1], or enough servers need to support ocsp stapling that the client can just reject connections that don't include it. And unfortunately, there was never a significant uptake for servers, partly because there wasn't really any incentive to implement OCSP stapling. Maybe if there was a TLS 2.0 (or some other standard) that required OCSP stapling and had other benefits as well, it could work.

[1]: the biggest problem with non-stapled OCSP is what to do if you don't get a response for the ocsp request. If you fail open, an attacker can intercept the request to prevent you from knowing the cert is revoked, but if you fail closed, then any issue with the connection to the ocsp server results in loss of service. And then there are also issues with additional latency to wait for the ocsp response, privacy leaks from the ocsp requests, etc.

saurik2• 10 months ago

How is this actually better (or conceptually even different) than just having the issuer's servers issue new certificates that only last 24 hours?

monkaiju2• 10 months ago

Has anyone gotten it to show as revoked?

userbinator• 10 months ago

Don't forget revocation checking = more centralised control, although they seem to have gone with very-short-lived certificates instead.

Dylan168074• 10 months ago

Don't forget revocation checking = more centralised contro

How so? Doesn't revocation have to be done by the same entity that issued the certificate?

perching_aix• 10 months ago

It's also literally a centralized trust model though. You know how the saying goes: if you're going to be a criminal, you may as well be the best one in town.

mholt6• 10 months ago

Revocation has many meanings. No central revocation authority is actually enforced by the BRs, as far as I know. Clients can do whatever they want. The CA can say a cert is revoked but no one has to care. Clients can also say a cert is revoked and then all their client instances start rejecting it. Most clients work this way now, like Safari -- they just distribute their own CRLs.

jofla_net• 10 months ago

Sometime last summer, I encountered a domain which WAS revoked. I was and am using Firefox, roughly v120, in Ubuntu and it threw up an unskippable error page, similar to those self signed pages in chrome. I did turn it off for hahas, in about:config, i believe it was an OCSP setting, security.OCSP.enabled to let me view the page.

However, this page, shows perfectly, so there must have been some differences between this and the domain I remember. Unfortunately, my domain has long since been reissued and I can't reproduce the block. The block also occurred in the latest Thunderbird for windows 7 interestingly.

synotna• 10 months ago

OCSP is deprecated for CRLs

Let's encrypt already EOLd OCSP

johnecheck• 10 months ago

I've always felt that the browser vendor + CA model was bad but this is next level embarrassing. How is the very root of trust in the internet so... untrustworthy?

kingstnap• 10 months ago

Revocation seems really nasty to deal with.

The whole chain of trust model is that your browser vouches for an authority that vouches for a website that everything is legit.

You can't just ducktape on an idea like that cert for "www.xyz" is totally legit unless I takesies-backies'd my vouch at some point, so just double-check.

If you want that sort of "continuous" trust scheme, then what makes more sense is something like having short-lived certificates.

snailmailman• 10 months ago

is this specific page supposed to show as revoked? its not showing as revoked for me in firefox, but https://revoked.badssl.com/ does so i know my browser is doing revocation checking. I'm curious whats happening here.

zephyreon6• 10 months ago

https://revoked.badssl.com

This loads fine in Safari on iOS 26 lol.

monkaiju2• 10 months ago

Also in Fennec 129...

tsimionescu• 10 months ago

revoked.badssl.com is showing up for me in Firefox on mobile just fine, so perhaps there is some nondeterminism here in some way? To be fair, this would be even more bizarre...

lucumo2• 10 months ago

Interestingly Chrome 140.0.7339.51 on Android 16 blocks it with a net::ERR_CERT_REVOKED error.

I always thought Chrome didn't block them and that revocation was pretty much dead.

lucumo2• 10 months ago

To clarify, https://revoked.badssl.com/ is the one being blocked. https://revoked-isrgrootx1.letsencrypt.org/ shows just fine.

prirai• 10 months ago

The certificate expiry is Dec 2025 so it's valid.

mholt6• 10 months ago

This page is to demonstrate that revocation is broken. There is no central revocation authority. Anyone can publish a revocation list, whether it's a CA or client vendors or Joe from his mom's basement.

I'm using the term "revocation list" loosely, as it can be as simple as a list of public keys to distrust. Client software can use any revocation list they want, AFAIK.

bawolff• 10 months ago

That's because revocation checking (if it ocsp) is something that sounds good at a glance but is actually quite a bad idea. Not doing live revocation checking is definitely the right choice for browsers to make. It doesn't protect against real threats and is terrible for privacy.

usr11063• 10 months ago

Details: https://www.ssllabs.com/ssltest/analyze.html?d=revoked-isrgr...

Edit: Their details are not correct: They claim the browsers would not trust it, but in practice they do.

sugarpimpdorsey3• 10 months ago

Their details are not correct: They claim the browsers would not trust it

But their details ARE correct. It says the certificate is revoked, which it is. It's up to the individual browser to act upon that (which most don't).

usr11063• 10 months ago

As part of their details they mention browser behavior. And that part is incorrect.

hannob• 10 months ago

For the people wondering why this does not show up as revoked in their browser: I believe the way the current revocation systems work is that browsers compile centralized lists of revoked certificates, but they do not contain all revoked certs, but only ones that indicate some form of security issue.

Certificates can be revoked with various revocation reasons, however, it looks this one has no specific revocation reason listed in the CRL. For a certificate that was revoked with a reason of "Key Compromise", things would be different, and most browsers would probably reject it.

yegle2• 10 months ago

[citation needed]

mholt6• 10 months ago

The citation is that that is Hanno Böck.

dadrian2• 10 months ago

https://dadrian.io/blog/posts/revocation-aint-no-thang/

NoahZuniga• 10 months ago

I believe I remember reading that chrome has a seperate system for revoking CA certificates, where they have to do a manual rollout, but propagation time is pretty fast.

jschanck2• 10 months ago

Firefox / CRLite includes all revocations. The issue with this particular certificate is that the CRLite backend is behind on ingesting both of the CT logs that it appears in (Digicert wyvern2025h2 [1] and Let's Encrypt oak2025h2). So from CRLite's perspective the certificate doesn't exist yet.

In the very near future, CAs are going to start embedding signed CT timestamps from "static CT" logs [2]. Once that happens, the CRLite backend will be aware of certificates within minutes of issuance.

[1] The wyvern2025h2 shard had an outage last week, which is also part of the problem here https://groups.google.com/a/chromium.org/g/ct-policy/c/XpmIf....

[2] https://github.com/C2SP/C2SP/blob/main/static-ct-api.md

jschanck2• 10 months ago

Actually, the story in this case is a bit more complicated than I initially thought: https://github.com/mozilla/crlite/issues/367.

BobbyTables2• 10 months ago

What would be the point of accepting a certificate that was revoked for non-security reasons?

Might as well not even revoke it…

If a CA issues a certificate to the wrong entity, they won’t have knowledge of a key compromise as there is no such thing in this case — they only know that they issued something wrong…

thayne4• 10 months ago

Several years ago, I saw some documentation about specifying the locations of CRLs in some proxy software. My first thought was "surely I have some of those on the system for web PKI". I was wrong. That sent me down a deep dark rabbit hole of how revocations are normally handled, at the bottom of which was the conclusion that most software does nothing, because it is just too hard.

Firefox has a project (crlite) that uses bloom filters to make crls more practical, but it is still experimental. I think we are a long ways out from the technology being widely used across the industry.

It turns out it is easier to significantly reduce the validity time of webpki certs than solve the problem of distributing distrbuting a list of revoked certificates. Although the former actually helps a lot with the latter, as it reduces the size of said list.

mholt6• 10 months ago

Context: WebPKI revocation is broken. It didn't have to be [0], but it always has been, and likely always will be, now that the industry is moving to short-lived certificates.

Let's Encrypt is now offering a profile for 6-day certificates: https://letsencrypt.org/docs/profiles/#shortlived

With such short-lived certificates, revocation effectively becomes a non-issue.

[0]: OCSP Stapling (esp. with Must-Staple) is actually pretty effective at distributing revocation information in a timely, secure, private manner. There were no real downsides to the spec, which is why Caddy has supported automatic OCSP stapling since, gosh, I think 2016 or so. The problem is that most other web servers didn't -- and still don't -- implement it well [1], making OCSP (without the stapling) a persistent privacy problem. Additionally, many client vendors want to choose what certificates count as "revoked" now, so they use their own CRLs, making OCSP entirely useless, since they only check their own CRLs.

[1] https://gist.github.com/sleevi/5efe9ef98961ecfb4da8 -- most servers have such a bad implementation of OCSP stapling that it makes sites less reliable, not more.

strcat• 10 months ago

Other web servers have a reliable implementation of OCSP stapling via their support for loading the OCSP response from an external file. It isn't as convenient as having it built-in but it works well.

GrapheneOS used https://github.com/tomwassenberg/certbot-ocsp-fetcher for years to provide reliable OCSP stapling for nginx prior to Let's Encrypt dropping OCSP support. We used Must-Staple through that for years.

TLS ticket key rotation also generally needs to be handled externally in a noswap tmpfs to avoid the keys being lost when restarting service, especially if syncing them across multiple nodes providing the same service is desired. Syncing them across nodes also allows preserving them across reboots while still only having them in-memory.

Let's Encrypt is now offering a profile for 6-day certificates: https://letsencrypt.org/docs/profiles/#shortlived

Only the default classic and opt-in tlsserver profiles are available. The allowlist mentioned there doesn't really seem to exist yet. The tlsserver profile has the same changes as shortlived without dropping 90 days to 160 hours. Both tlsserver and shortlived drop support for clients without SNI support which are unfortunately still very common for non-web usage. We found we can't deploy tlsserver for our SMTP federation (port 25) or SUPL server without having a fallback certificate for clients without SNI support. Since shortlived drops non-SNI client support, not everyone will be able to use it. It would be nice if there were 2 variants of it instead since client functionality is typically not within the control of servers.

Let's Encrypt dropped OCSP support before they had the replacement of short-lived certificates deployed. It would have been nice if OCSP support was only dropped after shortlived was enabled for production usage, but it's too late for that now. If it was possible to start using shortlived today, we would.

selinkocalar• 10 months ago

Certificate revocation has always been broken in practice. OCSP is slow. It creates privacy issues. CRL distribution is a mess. Honestly most implementations just fail open when they can't reach the revocation server. The real problem is that revocation assumes a perfect world where compromised certificates are immediately reported and revoked. In reality, most breaches go undetected for months…

geldedus• 10 months ago

Unclear message on the page. I still don't know if the certificate is revoked or not.

inahga• 10 months ago

For those (i.e. me) who were concerned that the cert wasn't actually revoked, it is.

https://crt.sh/?id=20924740030

    $ curl -s http://r13.c.lencr.org/105.crl | openssl crl -noout -text | grep -A1 899DE8
        Serial Number: 055B8B1F23D5BCF09DD8E9CAF8798F899DE8
            Revocation Date: Sep 10 16:00:16 2025 GMT

Not all browsers perform revocation checking

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