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Vulnerability record · CVE-2026-28802 · published 6 March 2026

CVE-2026-28802: Authlib improper verification of cryptographic signature vulnerability

Authlib · Authlib

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.

7.7 CVSS 4.0 High EPSS 0.55% · top 56.4% CWE-347 · Improper verification of cryptographic signature
7.7CVSS 4.0 base score
0.55%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
12References, 1 tagged exploit
10 Sep 2026Last modified by NVD

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: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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/authlib/authlib/commit/a61c2acb807496e67f32051b5f1b1d5ccf8f0a75 Patch
https://github.com/authlib/authlib/commit/b87c32ed07b8ae7f805873e1c9cafd1016761df7 Patch
https://github.com/authlib/authlib/security/advisories/GHSA-7wc2-qxgw-g8gg ExploitVendor Advisory
https://access.redhat.com/errata/RHSA-2026:19375
https://access.redhat.com/errata/RHSA-2026:4942
https://access.redhat.com/errata/RHSA-2026:5168
https://access.redhat.com/errata/RHSA-2026:5665
https://access.redhat.com/errata/RHSA-2026:6309
https://access.redhat.com/errata/RHSA-2026:6568
https://access.redhat.com/security/cve/CVE-2026-28802
https://bugzilla.redhat.com/show_bug.cgi?id=2445120
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-28802.json

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-28802), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.