Is CVE-2025-59420 actively exploited?

CVE-2025-59420 has no public evidence of in-the-wild exploitation as of 2025-11-03.

What is the CVSS score for CVE-2025-59420?

CVE-2025-59420 has a CVSS score of 7.5 (HIGH severity). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

How do I patch CVE-2025-59420?

Patch guidance is available from authlib security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2025-59420.

Fix CVE-2025-59420 - HIGH authlib authlib

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.

CVSS Metrics

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Attack Vector: network
Complexity: low
Privileges: none
User Action: none
Scope: unchanged
Confidentiality: none
Integrity: high
Availability: none
Weaknesses: CWE-345 CWE-863 · Incorrect Authorization CWE-345

Metadata

Primary Vendor: AUTHLIB
Published: 9/22/2025
Last Modified: 11/3/2025
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

Affected Products

authlib : authlib

Remediation Guidance

Executive Summary

Cite this page

CVE-2025-59420. CVEDatabase.com. Retrieved 1 May 2026. https://cvedatabase.com/cve/CVE-2025-59420

View on NIST NVD

CVE-2025-59420 vulnerability