CVE-2025-61920 – Authlib is vulnerable to Denial of Service via Oversized JOSE Segments

CVE ID : CVE-2025-61920

Published : Oct. 10, 2025, 8:15 p.m. | 23 minutes ago

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.

Severity: 7.5 | HIGH

Visit the link for more details, such as CVSS details, affected products, timeline, and more…