CVE-2026-28802

CRITICAL9.8

Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification

Published Mar 6, 2026

Modified 1 months ago

Details

Authlib is a Python library which builds OAuth and OpenID Connect servers. From version 1.6.5 to before version 1.6.7, previous tests involving passing a malicious JWT containing alg: none and an empty signature was passing the signature verification step without any changes to the application code when a failure was expected.. This issue has been patched in version 1.6.7.

References

WEB

https://github.com/authlib/authlib/commit/a61c2acb807496e67f32051b5f1b1d5ccf8f0a75

WEB

https://github.com/authlib/authlib/commit/b87c32ed07b8ae7f805873e1c9cafd1016761df7

WEB

https://github.com/authlib/authlib/security/advisories/GHSA-7wc2-qxgw-g8gg

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-28802

CVSS Analysis

CVSS v4.0

7.7