https://vulnerability.circl.lu/rss/recent/all/10 Most recent entries from all 2026-09-29T22:15:45.999247+00:00 Vulnerability-Lookup info@circl.lu python-feedgen Contains only the most 10 recent entries. https://vulnerability.circl.lu/vuln/cve-2026-71554 CVE-2026-71554 — h2: Duplicate Host header could facilitate request smuggling 2026-09-29T22:15:46.197661+00:00

Affected: python-hyper h2

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.

 https://vulnerability.circl.lu/vuln/ghsa-6hr6-w5qg-qmwg GHSA-6hr6-w5qg-qmwg — h2: Duplicate Host header could facilitate request smuggling 2026-09-29T22:15:46.197786+00:00

Affected: PyPI: h2

### Impact h2 <=4.4.0 accepts request header blocks containing more than one Host header, and forwards 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, which is a request smuggling primitive (CWE-444).

### Patches Patched and fixed in v4.4.1

### Workarounds Users of the h2 library are advised to check and follow HTTP semantics best practices in their application code. h2 provides best effort sanity checks, but ultimately the calling code is responsible to ensure proper and safe usage of HTTP/2 as provided by h2, hyperframe, and hpack.

### References Similar to the previously disclosed and fixed duplicate content-length issue.

 https://vulnerability.circl.lu/vuln/pysec-2026-3628 PYSEC-2026-3628 — h2: Duplicate Host header could facilitate request smuggling 2026-09-29T22:15:46.197851+00:00

Affected: PyPI: h2

### Impact h2 <=4.4.0 accepts request header blocks containing more than one Host header, and forwards 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, which is a request smuggling primitive (CWE-444).

### Patches Patched and fixed in v4.4.1

### Workarounds Users of the h2 library are advised to check and follow HTTP semantics best practices in their application code. h2 provides best effort sanity checks, but ultimately the calling code is responsible to ensure proper and safe usage of HTTP/2 as provided by h2, hyperframe, and hpack.

### References Similar to the previously disclosed and fixed duplicate content-length issue.