CVE-2026-28490
Medium
Description
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.
SeverityMedium
CVSS6.5
Exploit probability—
ProductAuthlib
PublishedMar 16, 2026
First seenMar 16, 2026
Weakness typeCWE-203CWE-203CWE-327CWE-327
How to fix
Update
- authlib authlib1.6.9 or later
- authlib1.6.9 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| authlib authlib | v < 1.6.9 | 1.6.9 |
| authlibPyPI | v < 1.6.9 | 1.6.9 |
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