Documentation and ramblings of Daniel Stenberg, founder and lead developer of curl.
Visit daniel.haxx.se → On Hacker News Dec 2010 – Aug 2026
Software Engineering 58Security & Privacy 21Networking & Internet 13Life, Learning & Writing 12Tech Industry & Business 12Web & Frontend 10
The curl project will not accept or otherwise handle any vulnerability reports during the month of July 2026. We call it the curl summer of bliss. curl's submission form on Hackerone will be paused starting July 1, 2026. Summer of bliss starts: July 1, 2026. 00:00 CEST Submissions resume: August 3 2026. 09:00 CEST The…
yes, as in singular one. Back in April 2026 Anthropic caused a lot of media noise when they concluded that their new AI model Mythos is dangerously good at finding security flaws in source code. Apparently Mythos was so good at this that Anthropic would not release this model to the public yet but instead … Continue…
tldr: work has started to make Hyper work as a backend in curl for HTTP. curl and its data transfer core, libcurl, is all written in C. The language C is known and infamous for not being memory safe and for being easy to mess up and as a result accidentally cause security problems. At … Continue reading rust in curl…
Back in December I got a desperate email from this person. A woman who said her Instagram had been hacked and since she found my contact info in the app she mailed me and asked for help. I of course replied and said that I have nothing to do with her being hacked but I … Continue reading “Subject: Urgent Warning” →
-- "Have you ever detected anyone trying to add a backdoor to curl?" -- "Have you ever been pressured by an organization or a person to add suspicious code to curl that you wouldn't otherwise accept?" -- "If a crime syndicate would kidnap your family to force you to comply, what backdoor would you be … Continue…
I have held back on writing anything about AI or how we (not) use AI for development in the curl factory. Now I can't hold back anymore. Let me show you the most significant effect of AI on curl as of today - with examples. Bug Bounty Having a bug bounty means that we offer … Continue reading The I in LLM stands for…
In association with the release of curl 8.4.0, we publish a security advisory and all the details for CVE-2023-38545. This problem is the worst security problem found in curl in a long time. We set it to severity HIGH. While the advisory contains all the necessary details. I figured I would use a few additional ……
On Friday January 21, 2022 I received this email. I tweeted about it and it took off like crazy. The email comes from a fortune-500 multi-billion dollar company that apparently might be using a product that contains my code, or maybe they have customers who do. Who knows? My guess is that they do this … Continue…
Thursday, September 22nd 2016. An email popped up in my inbox. Subject: ares_create_query OOB write As one of the maintainers of the c-ares project I'm receiving mails for suspected security problems in c-ares and this was such a one. In this case, the email with said subject came from an individual who had reported a…
"the overall impression of the state of security and robustness of the cURL library was positive." I asked for, and we were granted a security audit of curl from the Mozilla Secure Open Source program a while ago. This was done by Mozilla getting a 3rd party company involved to do the job and footing … Continue…
Let me tell you a story about how Windows users are deleting files from their installation and as a consequence end up in tears. Background The real and actual curl tool has been shipped as part of Windows 10 and Windows 11 for many years already. It is called curl.exe and is located in the … Continue reading deleting…
tldr: Apple thinks it is fine. I do not. On December 28 2023, bugreport 12604 was filed in the curl issue tracker. We get a lot issues filed most days so this fact alone was hardly anything out of the ordinary. We read the reports, investigate, ask follow-up questions to see what we can learn … Continue reading the…
Some time ago I mentioned that we went through the curl source code and eventually got rid of all strncpy() calls. strncpy() is a weird function with a crappy API. It might not null terminate the destination and it pads the target buffer with zeroes. Quite frankly, most code bases are probably better off completely ……
This is a story consisting of several little building blocks and they occurred spread out in time and in different places. It is a story that shows with clarity how our current system with CVE Ids and lots of power given to NVD is a completely broken system. CVE-2020-19909 On August 25 2023, we got … Continue reading…
During October 2015 the curl web site sent out 1127 gigabytes of data. This was the first time we crossed the terabyte limit within a single month. Looking at the stats a little closer, I noticed that in July 2015 a particular single package started to get very popular. The exact URL was…
A few years years ago the curl project signed up and became a CNA. This means that we are masters of and can allocate our own CVE identifiers. For any security problems within our territory, it is we who decides if the issue should get a CVE or not. No more bogus CVEs. 57 CVEs … Continue reading a CVE dispute →
"given enough eyeballs, all bugs are shallow" The saying (also known as Linus' law) doesn't say that the bugs are found fast and neither does it say who finds them. My version of the law would be much more cynical, something like: "eventually, bugs are found", emphasizing the 'eventually' part. (Jim Zemlin apparently…
I spent a lot of time and effort digging up the numbers and facts for this post! Lots of people keep referring to the awesome summary put together by a friendly pseudonymous "Tim" which says that "53 out of 95" (55.7%) security flaws in curl could've been prevented if curl had been written in Rust. … Continue reading…
Don't trust. Verify. I could not resist making a fake book cover Here follows a brief description on how you can detect if the curl package would ever make an xz. xz (and its library liblzma) was presumably selected as a target because it is an often used component and by extension via systemd it … Continue reading…
There is something about having your product installed in over twenty billion instances all over the world and even out of the globe. In my case it helps me remain focused on and committed to working on the security aspects of curl. Ideally, we will never have our heartbleed moment. Security is also a generally ……
On the completely impossible situation of blocking the Tor .onion TLD to avoid leaks, but at the same time not block it to make users able to do what they want. dot-onion leaks The onion TLD is a Tor specific domain that does not mean much to the world outside of Tor. If you try … Continue reading Leeks and leaks →