CVE-2025-59420 (GCVE-0-2025-59420)
Vulnerability from cvelistv5
Published
2025-09-22 17:28
Modified
2025-11-03 17:45
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CWE
  • CWE-345 - Insufficient Verification of Data Authenticity
  • CWE-863 - Incorrect Authorization
Summary
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.
References
Impacted products
Vendor Product Version
authlib authlib Version: < 1.6.4
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