CVE-2026-28490: Authlib

Medium severity, CVSS 6.5. EPSS: 0.2% chance of exploitation in the next 30 days.

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a cryptographic padding oracle vulnerability was identified in the Authlib Python library concerning the implementation of the JSON Web Encryption (JWE) RSA1_5 key management algorithm. Authlib registers RSA1_5 in its default algorithm registry without requiring explicit opt-in, and actively destroys the constant-time Bleichenbacher mitigation that the underlying cryptography library implements correctly. This issue has been patched in version 1.6.9.

Affected products

• Authlib Authlib: before 1.6.9 (fixed in 1.6.9)

Published 2026-03-16. Last modified 2026-06-17.