CVE-2025-61920
Publication date 13 October 2025
Last updated 13 October 2025
Ubuntu priority
Cvss 3 Severity Score
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.
Status
Package | Ubuntu Release | Status |
---|---|---|
python-authlib | 25.10 questing |
Needs evaluation
|
25.04 plucky |
Needs evaluation
|
|
24.04 LTS noble |
Needs evaluation
|
|
22.04 LTS jammy |
Needs evaluation
|
Severity score breakdown
Parameter | Value |
---|---|
Base score |
|
Attack vector | Network |
Attack complexity | Low |
Privileges required | None |
User interaction | None |
Scope | Unchanged |
Confidentiality | None |
Integrity impact | None |
Availability impact | High |
Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |