CVEvulnerability

CVE-2025-61920

7.5 HIGH Published 2025-10-10 Modified 2026-10-19 Official page ↗
Status
Modified
Published
2025-10-10
Last modified
2026-10-19
Assigner
[email protected]
CVSS 3.1 ([email protected])
7.5 HIGH — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weaknesses
CWE-20, CWE-400, CWE-770

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.

Affected configurations

• authlib authlib (< 1.6.5)

Related

Weakness · CWE (3)

  • CWE-20 Improper Input Validation weakness
  • CWE-400 Uncontrolled Resource Consumption weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling weakness

References