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CVE-2025-61920

7.5 · HIGH

Authlib is a Python library which builds OAuth and OpenID Connect servers.

Published Oct 10, 2025CWE-20EPSS 0.64%

Overview

CVE-2025-61920 is a high-severity vulnerability. It was published on October 10, 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 1.6.5, Authlib’s JOSE implementation accepts unbounded JWS/JWT header and signature segments. A remote attacker can craft a token whose base64url‑encoded header or signature spans hundreds of megabytes. During verification, Authlib decodes and parses the full input before it is rejected, driving CPU and memory consumption to hostile levels and enabling denial of service. Version 1.6.5 patches the issue. Some temporary workarounds are available. Enforce input size limits before handing tokens to Authlib and/or use application-level throttling to reduce amplification risk.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. 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.

References

GitHubgithub.com/authlib/authlib/commit/867e3f87b072347a1ae9cf6983cc8bbf88447e5eGitHubgithub.com/authlib/authlib/security/advisories/GHSA-pq5p-34cr-23v9Reflists.debian.org/debian-lts-announce/2025/10/msg00032.html

How CyberStrike helps

Frequently asked questions

What is CVE-2025-61920?

CVE-2025-61920 is a high-severity vulnerability. It was published on October 10, 2025 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-61920?

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-2025-61920?

Check the references section for vendor advisories, patches, and mitigation guidance. 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-2025-61920?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-61920 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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