Medium severity · published Mar 16, 2026
CVE-2026-28490
Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Oracle
6.5
CVSS
0.1%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 4% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AU
authlib · authlib
< 1.6.9 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28490
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-28490
Patch
https://github.com/authlib/authlib/commit/48b345f29f6c459f11c6a40162b6c0b742ef2e22
Product
https://github.com/authlib/authlib/releases/tag/v1.6.9
Exploit
https://github.com/authlib/authlib/security/advisories/GHSA-7432-952r-cw78
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