CVE-2026-28802
Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
CVSS Score
9.1
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-347 |
| Vendor | authlib |
| Product | authlib |
| Published | Mar 6, 2026 |
| Last Updated | Jul 20, 2026 |
Stay Ahead of the Next One
Get instant alerts for authlib authlib
Be the first to know when new critical vulnerabilities affecting authlib authlib are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
Affected Versions
authlib / authlib
>= 1.6.5, < 1.6.7
References
github.com: https://github.com/authlib/authlib/security/advisories/GHSA-7wc2-qxgw-g8gg github.com: https://github.com/authlib/authlib/commit/a61c2acb807496e67f32051b5f1b1d5ccf8f0a75 github.com: https://github.com/authlib/authlib/commit/b87c32ed07b8ae7f805873e1c9cafd1016761df7 access.redhat.com: https://access.redhat.com/security/cve/CVE-2026-28802 bugzilla.redhat.com: https://bugzilla.redhat.com/show_bug.cgi?id=2445120 security.access.redhat.com: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-28802.json access.redhat.com: https://access.redhat.com/errata/RHSA-2026:6309 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:4942 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:6568 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:19375 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:5665 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:5168