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CVE-2026-28802

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

Published: Mar 6, 2026Updated: Jul 20, 2026 Sources: CVE List NVD GHSA BDUCWE-347
9.8CRITICAL
NVD MITRE
EPSS Score
0.4%
Top 65.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
Not 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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:H
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
ООО «Ред Софт»
commercial·RUaka red soft
РЕД ОСOn-premOS
Operating Systems / linux-distro
Сообщество свободного программного обеспечения
oss-projectaka fsf
AuthlibLibraryLibrary
OSS Libraries / generic-library
PyPI
package-ecosystem
authlib
OSS Libraries

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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