[pocksuppet]

This attack is called "HTTP desync" or "request smuggling". It's often done intentionally by a client to try and spy on other clients' responses.

Every time you multiplex requests from multiple clients onto one upstream connection, you are probably vulnerable to this, because (despite its superficial simplicity) HTTP is just too complex to reliably match the requests and responses to upstream.

For example a desync can be triggered in some systems by having more than one Content-Length header, by mixing Content-Length with chunked encoding, or by passing an HTTP/2 header called Content-Length that doesn't match the actual content length.

Here's a DEF CON talk (6 years ago) on this topic: https://www.youtube.com/watch?v=w-eJM2Pc0KI

The same attack has been applied to SMTP by messing up the line endings surrounding the end-of-message delimiter, where it's called SMTP smuggling. It may also apply to other protocols.

[markasoftware]

Very true, this was likely an attack. Worth noting that mr kettle has done a defcon talk nearly every year on some variant of this attack, the most recent one titled "HTTP/1.1 must die" because he rightfully believes that switching to the binary headers of http/2 (specifically in reverse proxy connections to upstream servers) is the only way to systematically prevent these.

[albinowax_]

I’ll be back next month with a load of fresh vectors in “Can AI Do Novel Security Research? Meet the HTTP Terminator”

https://portswigger.net/research/talks?talkId=36

Maybe my last presentation on the topic! Possibly.

[bostik]

Or as the Risky Business guys crystallise it: "James Kettle breaks the internet. Again."

[pocksuppet]

Why the reference to AI? This looks like standard security research.

[albinowax_]

If you follow the link, the presentation abstract should hopefully answer that question!

If that doesn’t help I guess you’ll need to wait for the whitepaper to land but I can assure you I didn’t just do my normal research then add AI to the title for clicks :)