CVE-2026-21265

Secure Boot Certificate Expiration Security Feature Bypass Vulnerability

State: Published
Severity: 6.4 Medium
Published: Jan 13, 2026
Updated: Jul 30, 2026
Reserved: Dec 11, 2025

Description

Windows Secure Boot stores Microsoft certificates in the UEFI KEK and DB. These original certificates are approaching expiration, and devices containing affected certificate versions must update them to maintain Secure Boot functionality and avoid compromising security by losing security fixes related to Windows boot manager or Secure Boot. The operating system’s certificate update protection mechanism relies on firmware components that might contain defects, which can cause certificate trust updates to fail or behave unpredictably. This leads to potential disruption of the Secure Boot trust chain and requires careful validation and deployment to restore intended security guarantees.

Certificate Authority (CA) Location Purpose Expiration Date

Microsoft Corporation KEK CA 2011 KEK Signs updates to the DB and DBX 06/24/2026

Microsoft Corporation UEFI CA 2011 DB Signs 3rd party boot loaders, Option ROMs, etc. 06/27/2026

Microsoft Windows Production PCA 2011 DB Signs the Windows Boot Manager 10/19/2026

For more information see this CVE and Windows Secure Boot certificate expiration and CA updates.

Scores

CVSS	Score	Vector	Source
3.1	6.4 Medium	CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C	microsoft

Weaknesses

CWE-1329 Reliance on Component That is Not Updateable

Affected Products

Product	Versions
Windows 10 Version 1607Microsoft	10.0.14393.0 to before 10.0.14393.8783Affected
Windows 10 Version 1809Microsoft	10.0.17763.0 to before 10.0.17763.8276Affected
Windows 10 Version 21H2Microsoft	10.0.19044.0 to before 10.0.19044.6809Affected
Windows 10 Version 22H2Microsoft	10.0.19045.0 to before 10.0.19045.6809Affected
Windows 11 version 23H2Microsoft	10.0.22631.0 to before 10.0.22631.6491Affected
Windows 11 Version 23H2Microsoft	10.0.22631.0 to before 10.0.22631.6491Affected
Windows 11 Version 24H2Microsoft	10.0.26100.0 to before 10.0.26100.7623Affected
Windows 11 Version 25H2Microsoft	10.0.26200.0 to before 10.0.26200.7623Affected
Windows Server 2012Microsoft	6.2.9200.0 to before 6.2.9200.25868Affected
Windows Server 2012 (Server Core installation)Microsoft	6.2.9200.0 to before 6.2.9200.25868Affected
Windows Server 2012 R2Microsoft	6.3.9600.0 to before 6.3.9600.22968Affected
Windows Server 2012 R2 (Server Core installation)Microsoft	6.3.9600.0 to before 6.3.9600.22968Affected
Windows Server 2016Microsoft	10.0.14393.0 to before 10.0.14393.8783Affected
Windows Server 2016 (Server Core installation)Microsoft	10.0.14393.0 to before 10.0.14393.8783Affected
Windows Server 2019Microsoft	10.0.17763.0 to before 10.0.17763.8276Affected
Windows Server 2019 (Server Core installation)Microsoft	10.0.17763.0 to before 10.0.17763.8276Affected
Windows Server 2022Microsoft	10.0.20348.0 to before 10.0.20348.4648Affected
Windows Server 2022, 23H2 Edition (Server Core installation)Microsoft	10.0.25398.0 to before 10.0.25398.2092Affected
Windows Server 2025Microsoft	10.0.26100.0 to before 10.0.26100.32230Affected
Windows Server 2025 (Server Core installation)Microsoft	10.0.26100.0 to before 10.0.26100.32230Affected

References

Secure Boot Certificate Expiration Security Feature Bypass Vulnerabilityvendor-advisorypatch

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