MEDIUM 5.3 NVD
CVE-2026-71554
h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host hea
h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, providing a request smuggling primitive. This issue is fixed in version 4.4.1.
References
- https://github.com/python-hyper/h2/commit/292a40829feefda98c8509dcdbbb4a57af9bd6a6
- https://github.com/python-hyper/h2/security/advisories/GHSA-6hr6-w5qg-qmwg
This medium severity vulnerability with a CVSS score of 5.3 was published on 2026-08-06 via NVD.
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