Use of a broken or risky cryptographic algorithm in authlib - CVE-2026-28490
Published: March 17, 2026
Vulnerability identifier: #VU124063
CSH Severity: High
CVSS v4: 8.3 [CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-28490
CWE-ID: CWE-327
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to decrypt JWT tokens.
The vulnerability exists due to the JSON Web Encryption (JWE) implementation uses the RSA1_5 key management algorithm without requiring explicit opt-in and actively destroys the constant-time Bleichenbacher mitigation that the underlying cryptography library implements correctly. A remote attacker can decrypt JWT tokens used for authentication successful bypass authentication mechanisms use by OAuth and OpenID Connect servers.
Affected software
authlib
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Desktop 15
Python 3 Module
openSUSE Leap
Ubuntu
python-authlib (Ubuntu package)
python311-Authlib
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Desktop 15
Python 3 Module
openSUSE Leap
Ubuntu
python-authlib (Ubuntu package)
python311-Authlib
How to mitigate CVE-2026-28490
Install updates from vendor's website.
authlib - update to 1.6.9
python-authlib (Ubuntu package) - addressed in versions 0.15.5-1ubuntu0.1~esm2, 1.3.0-1ubuntu0.1~esm2, 1.6.7-1ubuntu0.1~esm1
python311-Authlib - update to 1.3.1-150600.3.17.1
python-authlib (Ubuntu package) - addressed in versions 0.15.5-1ubuntu0.1~esm2, 1.3.0-1ubuntu0.1~esm2, 1.6.7-1ubuntu0.1~esm1
python311-Authlib - update to 1.3.1-150600.3.17.1