🛡️ CVE-2026-71554 on Debian — python-h2

⚪ Unknown ✅ No Known Exploit OSV

N/A

CVSS Score

0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2026-71554 as tracked by Debian, for the package python-h2. No fixed version has been recorded for this distribution yet.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability low.

Weakness class

DEBIAN-CVE-2026-71554 is classified as CWE-444: HTTP Request Smuggling. A proxy and a server disagree on where one request ends, letting an attacker slip a second request past the front end.

Affected software

DEBIAN-CVE-2026-71554 is recorded against 1 package.

python-h2

Timeline and source

Published on 6 August 2026 and last revised on 8 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

Details

Severity Unknown

CVSS Score N/A

CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CWE N/A

Public Exploit ✅ No

Source OSV

Published 2026-08-06

Updated 2026-08-20

Modified 2026-08-08

Fix URL N/A

Affected Packages

Software	From version	Fixed in
python-h2	—	—

References

ADVISORY https://security-tracker.debian.org/tracker/CVE-2026-71554

🔗 NVD 🔗 Mitre

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