Is there a public exploit for CVE-2025-61920?

No public exploit for CVE-2025-61920 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2025-61920?

CVE-2025-61920 scores CVSS 7.5 (v3.1), rated high. EPSS puts the chance of exploitation in the next 30 days at 0.64%.

What does CVE-2025-61920 affect?

CVE-2025-61920 affects authlib authlib.

7.5 High

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

CVE-2025-61920

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.

Assessment

CVSS: 7.5 (v3.1)
Severity: High
EPSS: 0.64% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 10 October 2025
Last updated: 19 October 2026
Affected: authlib · authlib
Weakness: CWE-20, CWE-400, CWE-770
Assigner: security-advisories@github.com

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

At the source

References

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