Insufficient Verification of Data Authenticity Affecting python-authlib package, versions <0.15.5-1ubuntu0.1~esm1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-UBUNTU2204-PYTHONAUTHLIB-13045065
- published27 Feb 2026
- disclosed22 Sept 2025
Introduced: 22 Sep 2025
CVE-2025-59420 (opens in a new tab)How to fix?
Upgrade Ubuntu:22.04 python-authlib to version 0.15.5-1ubuntu0.1~esm1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream python-authlib package and not the python-authlib package as distributed by Ubuntu.
See How to fix? for Ubuntu:22.04 relevant fixed versions and status.
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’s JWS verification accepts tokens that declare unknown critical header parameters (crit), violating RFC 7515 “must‑understand” semantics. An attacker can craft a signed token with a critical header (for example, bork or cnf) that strict verifiers reject but Authlib accepts. In mixed‑language fleets, this enables split‑brain verification and can lead to policy bypass, replay, or privilege escalation. This issue has been patched in version 1.6.4.