Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

SummaryAuthlib’s JWS verification accepts tokens that declare unknown critical header parameters crit, violating RFC 7515 “must‑understand” semantics. An attacker can craft a signed token with a critical header for example, bork or cnf that strict verifiers reject but Authlib accepts. In...

Incorrect Authorization

Overview authlib is a library in building OAuth and OpenID Connect servers. Affected versions of this package are vulnerable to Incorrect Authorization via the deserializecompact function. An attacker can bypass intended authorization policies by crafting a signed token with unknown critical head...

PT-2025-38752

Name of the Vulnerable Software and Affected Versions Authlib versions prior to 1.6.4 Description Authlib’s JWS verification improperly handles tokens declaring unknown critical header parameters crit, violating RFC 7515 specifications. An attacker can create a signed token with a critical header...