# CVE-2025-61920: python-authlib: Authlib is a Python library which builds OAuth and OpenID Connect servers

CVE-2025-61920 is fixed in 3 products on 1 platform, first by DEBIAN-CVE-2025-61920, released October 10, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-61920
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0064
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 10, 2025

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python-Authlib opensuse-leap 15.6 | 1.3.1-150600.3.6.1 | [SUSE-SU-2025:3754-1](https://patchblox.com/security/data/fix/linux/suse-su-2025-3754-1.md) | Oct 23, 2025 |
| Linux | python-Authlib sles 15.6 | 1.3.1-150600.3.6.1 | [SUSE-SU-2025:3754-1](https://patchblox.com/security/data/fix/linux/suse-su-2025-3754-1.md) | Oct 23, 2025 |
| Linux | python-Authlib sles 15.7 | 1.3.1-150600.3.6.1 | [SUSE-SU-2025:3754-1](https://patchblox.com/security/data/fix/linux/suse-su-2025-3754-1.md) | Oct 23, 2025 |
| Linux | python-authlib Debian 12.15 (bookworm) | 1.2.0-1+deb12u1 | [DEBIAN-CVE-2025-61920](https://patchblox.com/security/data/fix/linux/debian-cve-2025-61920.md) | Oct 10, 2025 |
| Linux | python-authlib Debian 13.5 (trixie) | 1.6.0-1+deb13u1 | [DEBIAN-CVE-2025-61920](https://patchblox.com/security/data/fix/linux/debian-cve-2025-61920.md) | Oct 10, 2025 |
| Linux | python-authlib Debian 14 | 1.6.5-1 | [DEBIAN-CVE-2025-61920](https://patchblox.com/security/data/fix/linux/debian-cve-2025-61920.md) | Oct 10, 2025 |
| Linux | python3-authlib Ubuntu 22.04.1 LTS (jammy) | 0.15.5-1ubuntu0.1~esm1 | [python3-authlib 0.15.5-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-python3-authlib-0.15.5-1ubuntu0.1-esm1.md) | Oct 22, 2025 |
| Linux | python3-authlib Ubuntu 24.04.5 LTS (noble) | 1.3.0-1ubuntu0.1~esm1 | [python3-authlib 1.3.0-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-authlib-1.3.0-1ubuntu0.1-esm1.md) | Jan 8, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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