python-hyper/h11

python-hyper/h11

GitHubGitHub
GitHubgithub.com
h11.readthedocs.ioh11.readthedocs.io
Releases13
Frequency8 months 4 weeks
Last Release
Stars558
A pure-Python, bring-your-own-I/O implementation of HTTP/1.1
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CVE History

CVEPublishedCVSS v3CVSS v2
CVE-2025-43859↗
9.1 CRITICAL—

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.