CVE-2026-28802

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

Published Mar 6, 2026 CVSS 4.0 · 7.7 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-7wc2-qxgw-g8gg Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
History
Type Values Removed Values Added
CPEs cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Authlib
Authlib authlib
Vendors & Products Authlib
Authlib authlib
Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

threat_severity

Important

Type Values Removed Values Added
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.
Title Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
Weaknesses CWE-347
References
Metrics cvssV4_0

{'score': 7.7, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 10, 2026, 12:05 PM
Reserved
Mar 3, 2026, 2:25 PM
Status
Modified
Published
Mar 6, 2026, 7:16 AM
Modified
Sep 10, 2026, 1:18 PM
Severity
Important
Public date
Mar 6, 2026, 6:44 AM