Medium severity5.3GHSA Advisory· Published Aug 6, 2026· Updated Sep 18, 2026
CVE-2026-71554
CVE-2026-71554
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.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
h2PyPI | < 4.4.1 | 4.4.1 |
Affected products
20- osv-coords19 versionspkg:apk/chainguard/jupyter-all-spark-notebookpkg:apk/chainguard/authentik-fips-2026.2pkg:apk/chainguard/py3.12-prefect-fipspkg:apk/wolfi/mitmproxypkg:pypi/h2pkg:apk/chainguard/authentik-2026.5pkg:apk/chainguard/airflow-3pkg:apk/chainguard/py3.13-prefect-fipspkg:rpm/opensuse/python-h2&distro=openSUSE%20Leap%2016.0pkg:apk/chainguard/apache-beam-python-3.14-sdkpkg:apk/chainguard/authentik-2026.2pkg:apk/chainguard/mitmproxypkg:apk/chainguard/py3.11-prefect-fipspkg:apk/wolfi/airflow-3pkg:apk/chainguard/localstackpkg:apk/chainguard/open-webuipkg:apk/wolfi/open-webuipkg:apk/chainguard/authentik-fips-2026.5pkg:rpm/opensuse/python-h2&distro=openSUSE%20Tumbleweed
< 7.5.6_git20260807-r0+ 18 more
- (no CPE)range: < 7.5.6_git20260807-r0
- (no CPE)range: < 2026.2.6-r13
- (no CPE)range: < 3.8.1-r1
- (no CPE)range: < 12.2.3-r5
- (no CPE)range: < 4.4.1
- (no CPE)range: < 2026.5.6-r8
- (no CPE)range: < 3.3.1-r0
- (no CPE)range: < 3.8.1-r1
- (no CPE)range: < 4.2.0-160000.4.1
- (no CPE)range: < 2.75.0-r2
- (no CPE)range: < 2026.2.6-r13
- (no CPE)range: < 12.2.3-r5
- (no CPE)range: < 3.8.1-r1
- (no CPE)range: < 3.3.1-r0
- (no CPE)range: < 4.14.0-r21
- (no CPE)range: < 0.11.0-r2
- (no CPE)range: < 0.11.0-r2
- (no CPE)range: < 2026.5.6-r7
- (no CPE)range: < 4.4.1-1.1
- Range: <= 4.4.0
Patches
Vulnerability mechanics
References
3News mentions
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