Improper Verification of Cryptographic Signature Affecting python-authlib package, versions <0.15.5-1ubuntu0.1~esm2


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.55% (42nd percentile)

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  • Snyk IDSNYK-UBUNTU2204-PYTHONAUTHLIB-15688492
  • published17 Jul 2026
  • disclosed16 Mar 2026

Introduced: 16 Mar 2026

CVE-2026-27962  (opens in a new tab)
CWE-347  (opens in a new tab)

How to fix?

Upgrade Ubuntu:22.04 python-authlib to version 0.15.5-1ubuntu0.1~esm2 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream python-authlib package and not the python-authlib package as distributed by Ubuntu. See How to fix? for Ubuntu:22.04 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1