VDB
CVE-2026-71554
CVE-2026-71554
PUBLISHED
CVSS 5.3 MEDIUM
Reported by GitHub_M · Published August 6, 2026
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.
Risk Scores
CVSS 3.1
5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| python-hyper | h2 | < 4.4.1 |
| chainguard | localstack | 0, 0, 0 |
| python-hyper | h2 | < 4.4.1, < 4.4.1, < 4.4.1 |
| PyPI | h2 | 0 |
| chainguard | mitmproxy | 0, 0, 0 |
| wolfi | mitmproxy | 0, 0, 0 |
| chainguard | open-webui | 0, 0, 0 |
| chainguard | airflow-3 | 0, 0, 0 |
| chainguard | prefect-fips | 0, 0, 0 |
| chainguard | authentik-2026.5 | 0, 0, 0 |
| chainguard | authentik-2026.2 | 0, 0, 0 |
| wolfi | open-webui | 0, 0, 0 |
| chainguard | authentik-fips-2026.2 | 0, 0, 0 |
| chainguard | authentik-fips-2026.5 | 0, 0, 0 |
| chainguard | jupyter-all-spark-notebook | 0, 0, 0 |
| wolfi | airflow-3 | 0, 0, 0 |
| chainguard | apache-beam-python-3.14-sdk | 0, 0, 0 |
Timeline
- Aug 6, 2026 CVE Published
- Aug 7, 2026 EPSS Score
- Aug 7, 2026 Coalition ESS Score
- Aug 8, 2026 EPSS Score
- Aug 9, 2026 Security Advisory
- Aug 24, 2026 EPSS Score
- Aug 26, 2026 EPSS Score
- Aug 30, 2026 EPSS Score
- Sep 3, 2026 EPSS Score
- Sep 6, 2026 EPSS Score
- Sep 9, 2026 EPSS Score
- Sep 12, 2026 EPSS Score
References
- https://github.com/python-hyper/h2/security/advisories/GHSA-6hr6-w5qg-qmwg x_refsource_CONFIRM
- https://github.com/python-hyper/h2/commit/292a40829feefda98c8509dcdbbb4a57af9bd6a6 x_refsource_MISC
- https://nvd.nist.gov/vuln/detail/CVE-2026-71554 advisory
- https://github.com/advisories/GHSA-6hr6-w5qg-qmwg advisory