CVEvulnerability

CVE-2025-59420

7.5 HIGH Published 2025-09-22 Modified 2026-10-19 Official page ↗
Status
Modified
Published
2025-09-22
Last modified
2026-10-19
Assigner
[email protected]
CVSS 3.1 ([email protected])
7.5 HIGH — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weaknesses
CWE-345, CWE-863

Description

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 header (for example, bork or cnf) that strict verifiers reject but Authlib accepts. In mixed‑language fleets, this enables split‑brain verification and can lead to policy bypass, replay, or privilege escalation. This issue has been patched in version 1.6.4.

Affected configurations

• authlib authlib (< 1.6.4)

Related

Weakness · CWE (2)

  • CWE-345 Insufficient Verification of Data Authenticity weakness
  • CWE-863 Incorrect Authorization weakness

References