CVE-2025-61920
Fixed in a distro release EPSS <1%CVSS 7.5
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.
Products: authlib
Fixed upstream
| Ecosystem | Package | Fixed in |
|---|---|---|
| PyPI | authlib | 1.6.5 |
Distro releases
| Release | Package | Fixed in |
|---|---|---|
| Chainguard | mlflow | 3.4.0-r2 |
| Chainguard | mlflow-iamguarded-compat | 3.4.0-r2 |
| Debian 11 | python-authlib | 0.15.4-1+deb11u1 |
| Debian 12 | python-authlib | 1.2.0-1+deb12u1 |
| Debian 13 | python-authlib | 1.6.0-1+deb13u1 |
| Debian 14 | python-authlib | 1.6.5-1 |
| SUSE Linux Enterprise Module for Python 3 15 SP6 | python-Authlib | 1.3.1-150600.3.6.1 |
| SUSE Linux Enterprise Module for Python 3 15 SP7 | python-Authlib | 1.3.1-150600.3.6.1 |
| Ubuntu 25.10 | python-authlib | no fix |
| Ubuntu Pro 22.04 LTS | python-authlib | 0.15.5-1ubuntu0.1~esm1 |
| Ubuntu Pro 24.04 LTS | python-authlib | 1.3.0-1ubuntu0.1~esm1 |
| Ubuntu Pro 26.04 LTS | python-authlib | no fix |
| Wolfi | mlflow | 3.4.0-r2 |
| Wolfi | mlflow-iamguarded-compat | 3.4.0-r2 |
| openSUSE Leap 15.6 | python-Authlib | 1.3.1-150600.3.6.1 |
| openSUSE Tumbleweed | python-Authlib | 1.6.5-1.1 |