Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a library-level vulnerability was identified in the Authlib Python library concerning the validation of OpenID Connect (OIDC) ID Tokens. Specifically, the internal hash verification logic (_verify_hash) responsible for validating the at_hash (Access Token Hash) and c_hash (Authorization Code Hash) claims exhibits a fail-open behavior when encountering an unsupported or unknown cryptographic algorithm. This flaw allows an attacker to bypass mandatory integrity protections by supplying a forged ID Token with a deliberately unrecognized alg header parameter. The library intercepts the unsupported state and silently returns True (validation passed), inherently violating fundamental cryptographic design principles and direct OIDC specifications. This issue has been patched in version 1.6.9.
References
| Link | Resource |
|---|---|
| https://github.com/authlib/authlib/commit/b9bb2b25bf8b7e01512d847a95c1749646eaa72b | Patch |
| https://github.com/authlib/authlib/releases/tag/v1.6.9 | Product Release Notes |
| https://github.com/authlib/authlib/security/advisories/GHSA-m344-f55w-2m6j | Exploit Mitigation Vendor Advisory |
Configurations
History
17 Mar 2026, 20:40
| Type | Values Removed | Values Added |
|---|---|---|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.5 |
| References | () https://github.com/authlib/authlib/commit/b9bb2b25bf8b7e01512d847a95c1749646eaa72b - Patch | |
| References | () https://github.com/authlib/authlib/releases/tag/v1.6.9 - Product, Release Notes | |
| References | () https://github.com/authlib/authlib/security/advisories/GHSA-m344-f55w-2m6j - Exploit, Mitigation, Vendor Advisory | |
| CPE | cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:* | |
| First Time |
Authlib authlib
Authlib |
16 Mar 2026, 18:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-03-16 18:16
Updated : 2026-03-17 20:40
NVD link : CVE-2026-28498
Mitre link : CVE-2026-28498
CVE.ORG link : CVE-2026-28498
JSON object : View
Products Affected
authlib
- authlib
