CVE-2026-28802
Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
- State
- Published
- Severity
- 7.7 High
- Published
- Mar 6, 2026
- Updated
- Sep 10, 2026
- Reserved
- Mar 3, 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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 7.7 High | 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 | GitHub_M |
| 3.1 | 9.1 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | redhat-SADP |
Weaknesses
- CWE-347 Improper Verification of Cryptographic Signature
Affected Products
| Product | Versions |
|---|---|
authlibauthlib |
|
References
- https://github.com/authlib/authlib/security/advisories/GHSA-7wc2-qxgw-g8gg
- https://github.com/authlib/authlib/commit/a61c2acb807496e67f32051b5f1b1d5ccf8f0a75
- https://github.com/authlib/authlib/commit/b87c32ed07b8ae7f805873e1c9cafd1016761df7
- https://access.redhat.com/security/cve/CVE-2026-28802vdb-entry
- RHBZ#2445120issue-tracking
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-28802.json
- https://access.redhat.com/errata/RHSA-2026:6309vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:5665vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:4942vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:6568vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:19375vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:5168vendor-advisory
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