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CVE-2026-27962

9.1 · CRITICAL

Authlib is a Python library which builds OAuth and OpenID Connect servers.

Published Mar 16, 2026CWE-347EPSS 0.54%

Overview

CVE-2026-27962 is a critical-severity vulnerability. It was published on March 16, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.

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/authlib/authlib/commit/a5d4b2d4c9e46bfa11c82f85fdc2bcc0b50ae681GitHubgithub.com/authlib/authlib/releases/tag/v1.6.9GitHubgithub.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5Refaccess.redhat.com/errata/RHSA-2026:19375Refaccess.redhat.com/errata/RHSA-2026:24853Refaccess.redhat.com/errata/RHSA-2026:48085Refaccess.redhat.com/errata/RHSA-2026:5665Refaccess.redhat.com/errata/RHSA-2026:7314Refaccess.redhat.com/security/cve/CVE-2026-27962Refbugzilla.redhat.com/show_bug.cgi?id=2448164

How CyberStrike helps

Frequently asked questions

What is CVE-2026-27962?

CVE-2026-27962 is a critical-severity vulnerability. It was published on March 16, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-27962?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-27962?

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-2026-27962?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-27962 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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