Three decades of #curl - Daniel Stenberg at NDC Security 2026

https://youtu.be/_n2vN-Bgq4U

curl has passed both works in number of words...

I know you've always been curios. How does the #curl code base compare to a few great literary works of art when it comes to number of words?

Happy to be at service:

Having been around for a while in the project allows me to chime in and say things like...

"it has been possible to build #curl with zlib since 2002. It has always been optional. Still is."

docs/cmdline-opts: tidy up retry-connrefused by Aehmlo · Pull Request #21182 · curl/curl The current docs for --retry-connrefused have a couple of minor typos in them. This revision tweaks the documentation text slightly to improve clarity.

Welcome Alex Hamilton as #curl commit author 1461: https://github.com/curl/curl/pull/21182

curl is a CNA The curl project has been accepted as a CVE Numbering Authority (CNA) for vulnerabilities in all products directly made or managed by the project. If I’m counting correctly, we are the 351st CNA. The official announcement from Mitre states: _curl is now a CVE Numbering Authority (CNA) for all products made and managed by the curl project. This includes curl, libcurl, and trurl._ In plain English, this means that we will reserve and manage our own CVEs in the future directly against the CVE database with no middle man, and also that we have a scope for CVEs that is our territory: curl and libcurl. No one else can now register CVEs for our products – without involving us. (There’s an appeals process so someone can still actually file CVEs for issues even if we say no, but at least there’s a process where both sides will argue their points.) We do not particularly want to be a CNA but we hope that this move will make it harder to file more stupid curl CVEs in the future.

There are now more than 500 CNAs: https://www.cve.org/programorganization/cnas

When #curl became a CNA in January 2024, we became the 351st one.

https://daniel.haxx.se/blog/2024/01/16/curl-is-a-cna/

#curl is soon in the 13 tests/KLOC club. I offer bonus points for all PRs that take us closer!

Original post on mastodon.social

89 days into the year, the #curl project has received 72 security reports on Hackerone and ten additional ones over other channels. Close to one a day on average.

Compared to 2024, this is roughly 4x the volume.

The "obviously AI slop" rate has drastically gone down but the rate of actual […]

socks: add assertion for hostname length in SOCKS5 connect by MarkLee131 · Pull Request #21157 · curl/curl The hostname length is validated against 255 in socks5_req0_init() (line 607) before socks5_req1_init() casts it to unsigned char (line 813). The cast is safe because of the earlier check, but ther...

Welcome Kaixuan Li as #curl commit author 1460: https://github.com/curl/curl/pull/21157

socks: reject zero-length GSSAPI/SSPI tokens from proxy by gregkh · Pull Request #21159 · curl/curl A "broken" SOCKS5 proxy can send an invalid length of the encryption token, which could cause malloc(0) to be called, which is a "platform can do what it wants" potential proble...

Welcome Greg Kroah-Hartman @gregkh as #curl commit author 1459: https://github.com/curl/curl/pull/21159

commit week hour heatmap in the curl project - which hour of the week commits were authored

commit UTC week hour in #curl

https://github.com/curl/stats/pull/31

days-per-cmdline-option is a slightly scary new #curl graph I'm trying out here:

https://github.com/curl/stats/pull/30

A matrix heatmap in GitHub contribution style showing which days of which weeks curl has been released on - the most.

#curl release weekday heatmap. New graph by @recollir

Yes, we normally release on Wednesdays!

"Unfortunately in the bank where i work it is not easy to change the version, it requires lots of resources to retest." says reporter who uses a ten years old #curl version with a suspicious bug... The problem is not open source.

Don’t trust, verify Software and digital security should rely on _verification_ , rather than trust. I want to strongly encourage more users and consumers of software to verify curl. And ideally require that you could do at least this level of verification of other software components in your dependency chains. ## Attacks are omnipresent With every source code commit and every release of software, there are risks. Also entirely independent of those. Some of the things a widely used project can become the victim of, include… * _Jia Tan_ is a skilled and friendly member of the project team but is _deliberately_ merging malicious content disguised as something else. * An established committer might have been breached unknowingly and now their commits or releases contain tainted bits. * A rando convinced us to merge what looks like a bugfix but is a small step in a long chain of tiny pieces building up a planted vulnerability or even backdoor * Someone blackmails or extorts an existing curl team member into performing changes not otherwise accepted in the project * A change by an established and well-meaning project member that adds a feature or fixes a bug mistakenly creates a security vulnerability. * The website on which tarballs are normally distributed gets hacked and now evil alternative versions of the latest release are provided, spreading malware. * Credentials of a known curl project member is breached and misinformation gets distributed appearing to be from a _known_ and _trusted source_. Via email, social media or websites. Could even be this blog! * Something in this list is backed up by an online deep-fake video where a known project member seemingly repeats something incorrect to aid a malicious actor. * A tool used in CI, hosted by a cloud provider, is hacked and runs something malicious * While the primary curl git repository has a downtime, someone online (impersonating a curl team member?) offers a temporary “curl mirror” that contains tainted code. In the event any of these would happen, they could of course also happen in combinations and in a rapid sequence. ## You can verify curl, mostly in the shape of libcurl, runs in tens of billions of devices. Clearly one of the most widely used software components in the world. People ask me how I sleep at night given the vast amount of nasty things that _could_ occur virtually at any point. There is only one way to combat this kind of insomnia: do everything possible and do it openly and transparently. Make it a little better this week than it was last week. Do software engineering right. Provide means for everyone to verify what we do and what we ship. Iterate, iterate, iterate. If even just a few users verify that they got a curl release signed by the curl release manager and they verify that the release contents is untainted and only contains bits that originate from the git repository, then we are in a pretty good state. We need enough _independent_ outside users to do this, so that one of them can blow the whistle if anything at any point would look wrong. I can’t tell you who these users are, or in fact if they actually exist, as they are and must be completely independent from me and from the curl project. We do however provide all the means and we make it easy for such users to do this verification. ## We must verify The few outsiders who verify that nothing was tampered with in the releases can only validate that the releases are made from what exists in git. It is our own job to make sure that what exists in git is _the real thing_. The secure and safe curl. We must do _a lot_ to make sure that whatever we land in git is okay. Here’s a list of activities we do. 1. we have a consistent code style (invalid style causes errors). This reduces the risk for mistakes and makes it easier to debug existing code. 2. we ban and avoid a number of “sensitive” and “hard-to-use” C functions (use of such functions causes errors) 3. we have a ceiling for complexity in functions to keep them easy to follow, read and understand (failing to do so causes errors) 4. we review all pull requests before merging, both with humans and with bots. We link back commits to their origin pull requests in commit messages. 5. we ban use of “binary blobs” in git to not provide means for malicious actors to bundle encrypted payloads (trying to include a blob causes errors) 6. we actively avoid base64 encoded chunks as they too could function as ways to obfuscate malicious contents 7. we ban most uses of Unicode in code and documentation to avoid easily mixed up characters that look like other characters. (adding Unicode characters causes errors) 8. we document everything to make it clear how things are supposed to work. No surprises. Lots of documentation is tested and verified in addition to spellchecks and consistent wording. 9. we have thousands of tests and we add test cases for (ideally) every functionality. Finding “white spots” and adding coverage is a top priority. curl runs on countless operating systems, CPU architectures and you can build curl in billions of different configuration setups: not every combination is practically possible to test 10. we build curl and run tests in over two hundred CI jobs that are run for every commit and every PR. We do not merge commits that have unexplained test failures. 11. we build curl in CI with the most picky compiler options enabled and we never allow compiler warnings to linger. We always use `-Werror` that converts warnings to errors and fail the builds. 12. we run all tests using valgrind and several combinations of sanitizers to find and reduce the risk for memory problems, undefined behavior and similar 13. we run all tests as “torture tests”, where each test case is rerun to have every invoked fallible function call fail once each, to make sure curl never leaks memory or crashes due to this. 14. we run fuzzing on curl: non-stop as part of Google’s OSS-Fuzz project, but also briefly as part of the CI setup for every commit and PR 15. we make sure that the CI jobs we have for curl never “write back” to curl. They access the source repository read-only and even if they would be breached, they cannot infect or taint source code. 16. we run `zizmor` and other code analyzer tools on the CI job config scripts to reduce the risk of us running or using insecure CI jobs. 17. we are committed to always fix reported vulnerabilities in the following release. Security problems never linger around once they have been reported. 18. we document everything and every detail about all curl vulnerabilities ever reported 19. our commitment to never breaking ABI or API allows all users to easily upgrade to new releases. This enables users to run recent security-fixed versions instead of legacy insecure versions. 20. our code has been audited several times by external security experts, and the few issues that have been detected in those were immediately addressed 21. Two-factor authentication on GitHub is mandatory for all committers All this done in the open with full transparency and full accountability. Anyone can follow along and verify that we follow this. Require this for all your dependencies. ## Not paranoia We plan for the event when someone actually wants and tries to hurt us and our users really bad. Or when that happens by mistake. A successful attack on curl can in theory reach _widely_. This is not paranoia. This setup allows us to sleep well at night. _This is why users still rely on curl after thirty years in the making._ ## Documented I recently added a verify page to the curl website explaining some of what I write about in this post.

Don’t trust, verify

daniel.haxx.se/blog/2026/03/26/dont-tru...

#curl

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curl - Verify

This new page on the curl website explains how you can (should?) verify #curl, and a little what we do to verify what we do.

We can never be 100% safe, but we can try.

https://curl.se/docs/verify.html

curl distro discussion 2026 A command line tool and library for transferring data with URL syntax, supporting DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, MQTTS, POP3, POP3S, RTMP, RTMP...

This is the day of #curl distro meeting 2026.

github.com/curl/curl/wiki/curl-dist...

The Wild Calls

#blackandwhite #nature #plant #leaf #curl #beckon #garden #bwnature #blackandwhitephotography #blackandwhitenature

Screenshot of German-speaking OSGeo4W install window

In the latest release of OSGeo4W they list the #curl license as "non-open-source"... 🤔

Best Explanation of #Gradient, #Divergence and #Curl #Physics #Mathematics
youtube.com/watch

Ever wanted to flash a Linux distro directly from the internet without saving the image locally? This guide shows you how with `curl`, `wget`, and `dd` – but beware of the live system trap!

thepixelspulse.com/posts/how-to-flash-os-wi...

#curl #wget #dd

docs/VERIFY.md: verify curl by bagder · Pull Request #21085 · curl/curl Don't trust, verify! Explains how you can verify curl.

Don't trust, verify!

Explains how you can verify #curl.

https://github.com/curl/curl/pull/21085

RE: https://hachyderm.io/@kees/116282745861595200

Fun to see the Linux kernel follow in #curl's footsteps! 😎 (we removed the last strncpy from curl in late 2025)

curl: remove NTLM, SMB and local crypto implementations

Later this year, we are set to remove remove NTLM, SMB and local crypto implementations from #curl

https://curl.se/mail/lib-2026-03/0026.html

PHP Solution for Service Platform Interaction PHP & Web Development Projects for $250-750 USD. I’m looking for a robust PHP-based solution that can interact with existing user accounts on a service platform, navigate

#API #Backend #Development #cURL #JavaScript #MySQL #PHP #Software #Architecture #Web #Development

Origin | Interest | Match

curl goes git Just a few days ago the curl project turned twelve years old, and I decided that it was time for us to ditch our trusty old CVS setup and switch over to use git instead for source code control. ## Why Switch at All I’ve been very content with CVS over the years and in our small project we don’t really have any particularly weird or high demands on the version control software. Lately (like in recent years) I’ve dipped my toes into various projects that have been using git, and more and more over time I’ve learned to appreciate the little goodies that git does that CVS simply cannot. I’m then not even speaking about branches or merges etc that git does a whole lot better and easier than CVS, I’m in fact even more in love with git’s way to ease handling with diffs sent by email and its great way of keeping track of authors separately from the committer etc. git am and git commit –author are simply two very handy tools missing in CVS. ## Why Git So if we want to switch from CVS to another tool what would we chose? That wasn’t really the question in my case so I didn’t answer it. In my case, it was rather that I’ve been using git in several projects and it is used in some of the biggest projects I work with so it was some git’s features I wanted. I didn’t consider any of the other distributed version tools as quite frankly: they wouldn’t be much better for me than what CVS already is. I want to reduce the number of different tools I need, and I’m quite sure anyway that git is one of the top contenders even if I would do an actual comparison. So the choice to go git was quite selfish and done by me, but I felt that quite a few guys in the curl community supported this decision and very few actually believe remaining with CVS was a better idea. The fact that git itself uses libcurl for its HTTP access of course also proves its good taste! 🙂 ## How did the conversion go Very easy and swiftly. First, as I mentioned above we never used branches much so we basically had a linear development with a set of tags. I did an rsync of the full repo to get a local copy to work with, then I ran ‘git cvsimport’ on that to created a new repo. I did run it a couple of times to make sure I had done a correct mapping of all CVS user names to their git equivalents. Converting >10 years of CVS commits took roughly 10 minutes on my desktop machine so it wasn’t that tedious even. Once I had a local repo created with all authors looking good, I simply followed the instructions on github.com on how to add a remote origin to a local branch and when I pushed to that, git sent off all commits ever made to curl to the remote repo now exposed to the world from github.com. When that part was done, I did a quick read on the ‘git help daemon’ docs and 30 seconds later I had a local repo setup that is a mirror of the github one, so that users can still opt to get the code from haxx.se. ## Unchanged work flow Git allows different ways of working with the code, but I’ve decided that at least as a start we won’t change the way we work. I’ll offer all committers push rights to the master branch on the repository and we will simply all push to that, as our head development branch. We will prefer patches made with git format-patch sent to the mailing list, but as before you can still produce patches by diffing source code using extracted tarballs or whatever approach you prefer. All details on how to get the code for curl using git is available online.

16 years ago #curl officially switched over to using #git

https://daniel.haxx.se/blog/2010/03/23/curl-goes-git/

Anatomy of a ghost CVE > **“The Lord giveth and the Lord taketh away.”** > > Job 1:21 On March 16 2022, the curl security team received an email in which the reporter highlighted an Apple web page. _What can you tell us about this?_ I hadn’t seen it before. On this page with the title “About the security content of macOS Monterey 12.3”, said to have been published just two days prior, Apple mentions recent package upgrades and the page lists a bunch of products and what security fixes that were done for them in this update. Among the many products listed, curl is mentioned. This is what the curl section of the page looked like: Screenshot from March 17, 2022 In the curl project we always make all CVEs public with as much detail as we can possibly extract and provide about them. We take great pride in being the **best in class in security flaw information** and transparency. Apple listed four CVE fixed. The three first IDs we immediately recognized from the curl security page. The last one however, was a surprise. What was that? ## CVE-2022-22623 This is **not** a CVE published by the curl project. The curl project has in fact not shipped any CVE at all in 2022 (yet) so that’s easy to spot. When we looked at the MITRE registration for the ID, it also didn’t disclose any clues really. Not that it was expected to. It did show it was created on January 5 though, so it wasn’t completely new. Was it a typo? I compared this number to other recent CVE numbers announced from curl and I laid eyes on CVE-2021-22923 which had just two digits changed. Did they perhaps mean that CVE? The only “problem” with that CVE is that it was in regards to Metalink and I don’t think Apple ever shipped their curl package with metalink support so therefore they wouldn’t have fixed a Metalink problem. So probably not a typo for that number at least! I reached out to a friend at Apple as well with an email to Apple Product Security. ## Security is our number one priority In the curl project, we take security seriously. The news that there might be a security problem in curl that we haven’t been told about and that looks like it was about to get public sooner or later was of course somewhat alarming and something we just needed to get to the bottom of. It was also slightly disappointing that a large vendor and packager of curl _since over 20 years_ would go about it this way and jab this into our back. ## No source code Apple has not made the source code for their macOS 12.3 version and the packages they use in there public, so there was no way for us to run diffs or anything to check for the exact modifications that this claimed fix would’ve resulted in. ## Apple said so Several “security websites” (the quotes are there to indicate that clearly these sites are more security in the name than in reality) immediately posted details about this “vulnerability”. Some of them with CVSS scores and CWE numbers , explaining how this problem can hurt users. Obviously completely made up since none of that info was made available by any first party sources anywhere. Not from Apple and not from the curl project. If you now did a web search on that CVE number, several of the top search results linked to such sites providing details – obviously made up from thin air. As I think these sites don’t add much value to humanity, I won’t link to them here but instead I will show you a screenshot from such an article to show you what a made up CVE number posted by Apple can make people claim: Screenshot from exploitone.com At 23:28 (my time zone) on the 17th, my Apple friend responded saying they had forwarded the issue to “the right team”. The Apple Product Security team I also emailed about this issue, answered at 00:23 (still my time) on the 18th saying _“we are looking into this and will provide an update soon when we have more information.”_ ## The MITRE page got more details The MITRE CVE page from March 21st After the weekend passed with no response, I looked back again on the MITRE page for the CVE in question and it had then gotten populated with additional curl details; mentioning Apple as CNA and now featuring links back to the Apple page! Now it _really_ started to look like the CVE was something real that Apple (or someone) had registered but not told us about. It included real curl related snippets like this: > Multiple issues were addressed by updating to curl version 7.79.1. This issue is fixed in macOS Monterey 12.3. Multiple issues in curl. ## Please tell us more details On Monday the 21st, I continued to get questions about this CVE. Among others, from a member of a major European ISP’s CERT team curious about this CVE as they couldn’t find any specific information about this issue either and they were concerned they might have this vulnerability in the curl versions they run. They of course (rightfully) assumed that I would know about curl CVEs. It turns out that when a major company randomly mentions a new CVE, it actually has an impact on the world! ## Gone! At around 20:30 on March 21st, someone on Twitter spotted that the ghost CVE had been removed from Apple’s web page and it only listed three issues (and a mention that the section had been updated). At 21:39 I get an email response from Apple Product Security: > Thank you for reaching out to us about the error with this CVE on our security advisory. We’ve updated our site and requested that MITRE reject CVE-2022-22623 on their end. > Please let us know if you have any questions. Screenshot from March 21, 2022 The reject request to MITRE is expected to be slow so that page will remains showing the outdated data for a while longer. ## Exploit one When Apple had retracted the wrong CVE, I figured I should maybe try to get exploitone.com to remove their “article” to maybe at least stop one avenue of further misinformation about this curl “issue”. I tweeted (in perhaps a tad bit inflammatory manner): I get the feeling they didn’t quite understand my point. They replied: ## What happened? As I _had_ questions about Apple’s mishap, I replied (sent off 22:28 on the 21st, still only early afternoon on the US west coast), asking for details on what exactly had happened here. If it was a typo, then how come it got registered with MITRE? It’s just **so** puzzling and mysterious! When I’m posting this article on my blog (36 hours after I sent the question), I still haven’t gotten any response or explanation. I don’t expect to get any either, but if I do, I will update this post accordingly. ## Update March 26 exploitone.com updated their page at some point after my tweet to remove the mention of the imaginary CVE, but the wording remains very odd:

Today we celebrate four years since Apple pulled the ghost CVE prank on us:

daniel.haxx.se/blog/2022/03/23/anatomy-...

#curl

Number of options for curl_multi_setopt over time

How about a new graph? Number of options for curl_multi_setopt() over time

https://github.com/curl/stats/pull/27

#curl

Number of options for curl_multi_setopt over time

How about a new graph? Number of options for curl_multi_setopt() over time

https://github.com/curl/stats/pull/27

#curl

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Aircraft: Antonov An-26 B
2026-03-22 09:24:47 CDT
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