How We Found a Bug in the Hyper HTTP Library
Cloudflare, Monday, June 22nd, 2026
Cloudflare engineers found and fixed a longstanding race condition in the open-source hyper HTTP library.
While rearchitecting their Images binding, Cloudflare engineers uncovered a longstanding race condition in the open-source hyper HTTP library.
The bug truncated responses before they reached the outer pipeline, losing data when socket buffers filled during larger file transfers. Using kernel-level debugging with strace, the team determined that hyper was shutting down connections before flushing buffered data.
They contributed an upstream fix ensuring data is not lost during the flush-to-shutdown transition.