Python-hyper H2 vulnerabilities

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Published CVEs affecting Python-hyper H2: 1 record(s), with affected versions and fixes.

CVE-2026-71554 Medium · 5.3 CWE-444 Aug 6, 2026

h2: Duplicate Host header could facilitate request smuggling

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.