CVE-2025-43859 Information

Description

h11 is a Python implementation of HTTP/1.1. Prior to version 0.16.0 a leniency in h11’s parsing of line terminators in chunked-coding message bodies can lead to request smuggling vulnerabilities under certain conditions. This issue has been patched in version 0.16.0. Since exploitation requires the combination of buggy h11 with a buggy (reverse) proxy fixing either component is sufficient to mitigate this issue.

Reference

https://github.com/python-hyper/h11/commit/114803a29ce50116dc47951c690ad4892b1a36ed https://github.com/python-hyper/h11/security/advisories/GHSA-vqfr-h8mv-ghfj