Bug 2397460 (CVE-2025-59420) - CVE-2025-59420 authlib: Authlib RFC violation
Summary: CVE-2025-59420 authlib: Authlib RFC violation
Keywords:
Status: NEW
Alias: CVE-2025-59420
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2025-09-22 18:01 UTC by OSIDB Bzimport
Modified: 2025-09-22 21:48 UTC (History)
3 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2025-09-22 18:01:59 UTC 
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.
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