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CVE-2026-71554

5.3 · MEDIUM

h2 is a pure-Python implementation of a HTTP/2 protocol stack.

Published Aug 6, 2026CWE-444EPSS 0.42%

Overview

CVE-2026-71554 is a medium-severity vulnerability. It was published on August 6, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/python-hyper/h2/commit/292a40829feefda98c8509dcdbbb4a57af9bd6a6GitHubgithub.com/python-hyper/h2/security/advisories/GHSA-6hr6-w5qg-qmwg

How CyberStrike helps

Frequently asked questions

What is CVE-2026-71554?

CVE-2026-71554 is a medium-severity vulnerability. It was published on August 6, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-71554?

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-71554?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-71554?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-71554 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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