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
| Link | Resource |
|---|---|
| https://github.com/authlib/authlib/commit/6b1813e4392eb7c168c276099ff7783b176479df | Patch |
| https://github.com/authlib/authlib/security/advisories/GHSA-9ggr-2464-2j32 | Exploit Vendor Advisory |
Configurations
History
08 Oct 2025, 20:40
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://github.com/authlib/authlib/commit/6b1813e4392eb7c168c276099ff7783b176479df - Patch | |
| References | () https://github.com/authlib/authlib/security/advisories/GHSA-9ggr-2464-2j32 - Exploit, Vendor Advisory | |
| First Time |
Authlib authlib
Authlib |
|
| CPE | cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:* |
22 Sep 2025, 18:15
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2025-09-22 18:15
Updated : 2025-10-08 20:40
NVD link : CVE-2025-59420
Mitre link : CVE-2025-59420
CVE.ORG link : CVE-2025-59420
JSON object : View
Products Affected
authlib
- authlib