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CVE-2025-61920

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

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 7.5 · High · EPSS 0.6% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • authlib

    Versions
    • < 1.6.5: Affected

    No fix published

  • python-authlib Debian:12

    Versions
    • 1.2.0-1
    Affected ranges
    • ECOSYSTEM: < 1.2.0-1+deb12u1

    Update to 1.2.0-1+deb12u1

  • python-authlib Debian:13

    Versions
    • 1.6.0-1
    Affected ranges
    • ECOSYSTEM: < 1.6.0-1+deb13u1

    Update to 1.6.0-1+deb13u1

  • python-authlib Debian:14

    Versions
    • 1.6.0-1
    • 1.6.1-1
    • 1.6.3-1
    • 1.6.4-1
    Affected ranges
    • ECOSYSTEM: < 1.6.5-1

    Update to 1.6.5-1

  • authlib PyPI

    Versions
    • 0.1
    • 0.10
    • 0.11
    • 0.12
    • 0.12.1
    • 0.13
    • 0.14
    • 0.14.1
    • 0.14.2
    • 0.14.3
    • 0.15
    • 0.15.1
    • 0.15.2
    • 0.15.3
    • 0.15.4
    • 0.15.5
    • 0.15.6
    • 0.1rc0
    • 0.2
    • 0.2.1
    • 0.3
    • 0.4
    • 0.4.1
    • 0.5
    • 0.5.1
    • 0.6
    • 0.7
    • 0.8
    • 0.9
    • 1.0.0
    • 1.0.0a1
    • 1.0.0a2
    • 1.0.0b1
    • 1.0.0b2
    • 1.0.0rc1
    • 1.0.1
    • 1.1.0
    • 1.2.0
    • 1.2.1
    • 1.3.0
    • 1.3.1
    • 1.3.2
    • 1.4.0
    • 1.4.1
    • 1.5.0
    • 1.5.1
    • 1.5.2
    • 1.6.0
    • 1.6.1
    • 1.6.2
    • 1.6.3
    • 1.6.4
    Affected ranges
    • ECOSYSTEM: < 1.6.5

    Update to 1.6.5

  • python-authlib Ubuntu:Pro:22.04:LTS

    Versions
    • 0.15.4-1
    • 0.15.5-1
    Affected ranges
    • ECOSYSTEM: < 0.15.5-1ubuntu0.1~esm1

    Update to 0.15.5-1ubuntu0.1~esm1

  • python-authlib Ubuntu:Pro:24.04:LTS

    Versions
    • 1.2.1-1
    • 1.3.0-1
    Affected ranges
    • ECOSYSTEM: < 1.3.0-1ubuntu0.1~esm1

    Update to 1.3.0-1ubuntu0.1~esm1

  • python-authlib Ubuntu:25.10

    Versions
    • 1.5.1-1
    • 1.5.2-1
    • 1.6.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-authlib Ubuntu:Pro:26.04:LTS

    Versions
    • 1.6.0-1
    • 1.6.5-1
    • 1.6.6-1
    • 1.6.7-1
    • 1.6.7-1ubuntu0.1~esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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