CVE-2026-28802 HIGH

CVE-2026-28802: Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification

Vendor Authlib
Product authlib
Weakness CWE-347
Published March 6, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

7.7/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS 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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

March 6, 2026 CVE published
June 30, 2026 Record updated