CVE-2026-28498

EUVD-2026-12482

16.03.2026, 18:16

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.

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	Primary	7.5 HIGH	NETWORK	LOW	NONE	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Base Score

CVSS 3.x

EPSS Score

Percentile: 13%

Affected Products (NVD)

Vendor	Product	Version
authlib	authlib	𝑥 < 1.6.9

𝑥

= Vulnerable software versions

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
Red Hat	Red Hat Ansible Automation Platform 2.6	1774417022 ≤ 𝑥 < *	ADP
Red Hat	Red Hat Quay 3.1	1775169155 ≤ 𝑥 < *	ADP
Red Hat	Red Hat Quay 3.12	1775253092 ≤ 𝑥 < *	ADP
Red Hat	Red Hat Quay 3.15	1775169219 ≤ 𝑥 < *	ADP
Red Hat	Red Hat Quay 3.16	1775069491 ≤ 𝑥 < *	ADP
Red Hat	Red Hat Quay 3.16	1775169226 ≤ 𝑥 < *	ADP