CVE-2026-75509: Authlib Joserfc

Medium severity, CVSS 6.5. EPSS: 0.1% chance of exploitation in the next 30 days.

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.

Affected products

• Authlib Joserfc: before 1.7.3 (fixed in 1.7.3)

Published 2026-08-24. Last modified 2026-09-09.