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CVE-2026-71554

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-71554

Severity

5.3

Medium

CVSS V3

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Summary

h2: Duplicate Host header could facilitate request smuggling

Description

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

Affected packages

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