CVE-2026-28802
CRITICAL9.8EPSS 0.02%Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
Published: 3/4/2026Modified: 4/28/2026
Description
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.
Affected packages (2)
- Debian/python-authlibfrom 0
- PyPI/authlib>= 1.6.5, < 1.6.7
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P |
| osv | CVSS 3.1 | CRITICAL9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
References (6)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-28802
- ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2026-28802
- PATCHhttps://github.com/authlib/authlib
- WEBhttps://github.com/authlib/authlib/commit/a61c2acb807496e67f32051b5f1b1d5ccf8f0a75
- WEBhttps://github.com/authlib/authlib/commit/b87c32ed07b8ae7f805873e1c9cafd1016761df7
- WEBhttps://github.com/authlib/authlib/security/advisories/GHSA-7wc2-qxgw-g8gg