FKIE_CVE-2026-28498

Vulnerability from fkie_nvd - Published: 2026-03-16 18:16 - Updated: 2026-03-17 20:40
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Summary
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.
References
security-advisories@github.comhttps://github.com/authlib/authlib/commit/b9bb2b25bf8b7e01512d847a95c1749646eaa72bPatch
security-advisories@github.comhttps://github.com/authlib/authlib/releases/tag/v1.6.9Product, Release Notes
security-advisories@github.comhttps://github.com/authlib/authlib/security/advisories/GHSA-m344-f55w-2m6jExploit, Mitigation, Vendor Advisory
Impacted products
Vendor Product Version
authlib authlib *
To clipboard 

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      "value": "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."
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      "value": "Authlib es una biblioteca Python que construye servidores OAuth y OpenID Connect. Antes de la versi\u00f3n 1.6.9, se identific\u00f3 una vulnerabilidad a nivel de biblioteca en la biblioteca Python Authlib con respecto a la validaci\u00f3n de los tokens de ID de OpenID Connect (OIDC). Espec\u00edficamente, la l\u00f3gica interna de verificaci\u00f3n de hash (_verify_hash) responsable de validar las reclamaciones at_hash (Hash de Token de Acceso) y c_hash (Hash de C\u00f3digo de Autorizaci\u00f3n) exhibe un comportamiento fail-open al encontrar un algoritmo criptogr\u00e1fico no compatible o desconocido. Esta falla permite a un atacante eludir las protecciones de integridad obligatorias al suministrar un token de ID falsificado con un par\u00e1metro de encabezado alg deliberadamente no reconocido. La biblioteca intercepta el estado no compatible y devuelve silenciosamente True (validaci\u00f3n aprobada), violando inherentemente los principios fundamentales de dise\u00f1o criptogr\u00e1fico y las especificaciones directas de OIDC. Este problema ha sido parcheado en la versi\u00f3n 1.6.9."
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  "lastModified": "2026-03-17T20:40:37.573",
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