CVE-2025-59420
7.5 · HIGHOverview
CVE-2025-59420 is a high-severity vulnerability affecting authlib authlib. It was published on September 22, 2025 and has a CVSS 3.1 base score of 7.5 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from authlib. Update authlib to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| authlib | authlib | >= 0, < 1.6.4 | Affected |
Frequently Asked Questions
What is CVE-2025-59420?
CVE-2025-59420 is a high-severity vulnerability affecting authlib authlib. It was published on September 22, 2025 and has a CVSS 3.1 base score of 7.5 (HIGH).
How severe is CVE-2025-59420?
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2025-59420?
Check the references section for vendor advisories and patches from authlib. Update authlib to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2025-59420?
CyberStrike's AI-powered security agents can automatically detect CVE-2025-59420 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
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