Improper Validation of Integrity Check Value Affecting python-authlib package, versions <0.15.5-1ubuntu0.1~esm2


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.23% (14th percentile)

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  • Snyk IDSNYK-UBUNTU2204-PYTHONAUTHLIB-15688587
  • published17 Jul 2026
  • disclosed16 Mar 2026

Introduced: 16 Mar 2026

CVE-2026-28498  (opens in a new tab)
CWE-354  (opens in a new tab)
CWE-573  (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 library-level vulnerability was identified in the Authlib Python library concerning the validation of OpenID Connect (OIDC) ID Tokens. Specifically, the internal hash verification logic (_verify_hash) responsible for validating the at_hash (Access Token Hash) and c_hash (Authorization Code Hash) claims exhibits a fail-open behavior when encountering an unsupported or unknown cryptographic algorithm. This flaw allows an attacker to bypass mandatory integrity protections by supplying a forged ID Token with a deliberately unrecognized alg header parameter. The library intercepts the unsupported state and silently returns True (validation passed), inherently violating fundamental cryptographic design principles and direct OIDC specifications. This issue has been patched in version 1.6.9.

CVSS Base Scores

version 3.1