Vulnerability in Authlib
CVE-2026-28490
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (4.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 4th percentile — 4.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.000
Affected products
- Authlib — versions < 1.6.9
Weakness classification (CWE)
References
- github.com/authlib/authlib/security/advisories/GHSA-7432-952r-cw78 (Exploit, Mitigation, Vendor Advisory)
- github.com/authlib/authlib/commit/48b345f29f6c459f11c6a40162b6c0b742ef2e22 (Patch)
- github.com/authlib/authlib/releases/tag/v1.6.9 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-28490?
- CVE-2026-28490 is a medium-severity vulnerability in Authlib, classified under Observable Discrepancy. CVSS score: 6.5/10. Published 2026-03-16.
- How severe is CVE-2026-28490?
- Medium severity. CVSS v3 base score is 6.5 out of 10.