Authlib up to 1.6.8 signature verification

Summaryinfo

A vulnerability was found in Authlib up to 1.6.8 and classified as critical. Affected is an unknown function. The manipulation results in signature verification. This vulnerability is identified as CVE-2026-27962. The attack can be executed remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Authlib up to 1.6.8. Affected is an unknown code. The manipulation with an unknown input leads to a signature verification vulnerability. CWE is classifying the issue as CWE-347. The product does not verify, or incorrectly verifies, the cryptographic signature for data. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-27962 since 02/25/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. The technical details are unknown and an exploit is not available.

The vulnerability scanner Nessus provides a plugin with the ID 302533 (Linux Distros Unpatched Vulnerability : CVE-2026-27962), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.6.9 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (302533). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• Authlib

Version

• 1.6.0
• 1.6.1
• 1.6.2
• 1.6.3
• 1.6.4
• 1.6.5
• 1.6.6
• 1.6.7
• 1.6.8

Website

• Product: https://github.com/authlib/authlib/

CPE 2.3info

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CPE 2.2info

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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