CVE-2025-59420: PYSEC-2026-1200 - Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

CVE-2025-59420 · Severity: low · CVSS 3.1 · Published 2026-07-07

Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

Technologies: authlib (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2025-59420 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-59420 being exploited in the wild.
How severe is CVE-2025-59420?
Low severity, with a CVSS score of 3.1, published 7 July 2026.
Which products and versions are affected?
authlib (PyPI) ECOSYSTEM:introduced=0,fixed=1.6.4.
Is there a fix for CVE-2025-59420?
Yes. authlib (PyPI): upgrade to 1.6.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-59420?
Check whether you run authlib (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • authlib (PyPI): upgrade to 1.6.4 or later
    pip install "authlib>=1.6.4"

Affected products

  • authlib (PyPI) ECOSYSTEM:introduced=0,fixed=1.6.4

Identifiers

  • CVE-2025-59420
  • GHSA-9ggr-2464-2j32
  • PYSEC-2026-1200

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