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CVE-2026-28802

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

Published: Mar 6, 2026Updated: Mar 6, 2026 Sources: CVE List NVD GHSA BDUCWE-347
NVD MITRE
9.8CVSSCRITICAL
EPSS Score
0.3%
Top 74.8%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LC:HI:HA:H
Exploitability
AV:NAccess Vector
Network
AC:LAccess Complexity
Low
Impact
C:HConfidentiality
H
I:HIntegrity
H
A:HAvailability
H
Open in CVSS calculator →

Weaknesses

CWE-347

Affected Products

authlibauthlib
Library
OSS Libraries / generic-library
РЕД ОСООО «Ред Софт»
On-premOS
Operating Systems / linux-distro
AuthlibСообщество свободного программного обеспечения
On-prem
Operating Systems / linux-distro
authlibPyPIOSS Libraries
authliboss-projectOSS Librariesaka jose rfc
ооо «ред софт»commercialRUOperating Systemsaka red soft
сообщество свободного программного обеспеченияoss-projectOperating Systemsaka сообщество свободного программного обеспечения, fsf
pypipackage-ecosystemOSS Libraries

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

1 technique
Collection
View detailed technique mapping

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 6 more references View all →

Timeline

Published
Mar 6, 2026
Last Updated
Mar 6, 2026

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