CVE-2026-35042

The CVE concerns fast-jwt (up to and including 6.1.0) not validating the RFC 7515 §4.1.11 crit header parameter, causing tokens with an unknown crit extension to be accepted instead of rejected. Affected components are the fast-jwt library (Node.js) and related advisories (GHSA-hm7r-c7qw-ghp6) wi...

CVE-2026-32597 PyJWT accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)

PyJWT is a JSON Web Token implementation in Python. Prior to 2.12.0, PyJWT does not validate the crit Critical Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that PyJWT does not understand, the library accepts the token instead of rejecting...

Privilege Escalation

authlib is vulnerable to Privilege Escalation. The vulnerability is due to accepting tokens with unknown crit headers, where Authlib violates RFC 7515 rules, allowing attackers to craft signed tokens that bypass strict verifiers and potentially enable policy bypass or privilege escalation...

UBUNTU-CVE-2025-59420

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’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...

CVE-2025-59420 Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’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...

CVE-2025-59420 Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’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...

CVE-2025-59420

Authlib (Python) prior to 1.6.4 verifies JWS tokens with unknown critical header parameters (crit), violating RFC 7515 must-understand semantics. An attacker could craft a signed token that strict verifiers reject but Authlib accepts, enabling policy bypass, replay, or privilege escalation in mix...

CVE-2025-59420

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’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...

CVE-2025-59420 Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’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...

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

Summary Authlib’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...

GHSA-9GGR-2464-2J32 Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

Summary Authlib’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...