CVE-2026-28802

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

Published: Mar 6, 2026Updated: Sep 10, 2026 Sources: CVE List NVD GHSA BDUCWE-347

9.8CRITICAL

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:HConfidentiality

High

I:HIntegrity

High

A:HAvailability

High

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Weaknesses

CWE-347

Affected Products

authlib

oss-projectaka jose rfc

authlibLibrary

OSS Libraries / generic-library

package-ecosystem

commercial·RUaka red soft

РЕД ОСOn-premOS

Operating Systems / linux-distro

Сообщество свободного программного обеспечения

oss-projectaka fsf

AuthlibLibraryLibrary

OSS Libraries / generic-library

Exploitability

Official Patch Available

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique

Collection

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References

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

github.com

and 15 more references View all →

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