CVE-2026-28490CWE-203CWE-327

Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Oracle

High · published March 16, 2026

CVSS v4.0
8.3
EPSS
0%
Percentile
5.4
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
8.3 · HIGH
Vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
EPSS
0.00165 · 5.4th percentile
Weaknesses
CWE-203 · Observable Discrepancy; CWE-327 · Use of a Broken or Risky Cryptographic Algorithm
Published
2026-03-16T17:37Z
EPSS history
Timeline
  • 16 MAR 17:37Z
    Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Oracle
    cvelistv5