Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding

Executive Summary A critical 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 verifyhash responsible for validating the athash Access Token Hash and chash...

PT-2026-25790

Authlib and Affected Versions Authlib versions prior to 1.6.9 Description Authlib, a Python library for building OAuth and OpenID Connect servers, contains a flaw in its OpenID Connect OIDC ID Token validation logic. The internal hash verification function verify hash exhibits a fail-open behavio...