1. Home
  2. CVE Database
  3. CVE-2026-21265
MEDIUM · 6.4

CVE-2026-21265

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 ...

Vulnerability 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.

CVSS Score

6.4

MEDIUM

CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH

Affected Products

VendorProductVersions
MicrosoftWindows 10 1607< 10.0.14393.8783
MicrosoftWindows 10 1809< 10.0.17763.8276
MicrosoftWindows 10 21H2< 10.0.19044.6809
MicrosoftWindows 10 22H2< 10.0.19045.6809
MicrosoftWindows 11 23H2< 10.0.22631.6491
MicrosoftWindows 11 24H2< 10.0.26100.7623
MicrosoftWindows 11 25H2< 10.0.26200.7623
MicrosoftWindows Server 2012-
MicrosoftWindows Server 2016< 10.0.14393.8783
MicrosoftWindows Server 2019< 10.0.17763.8276
MicrosoftWindows Server 2022< 10.0.20348.4648
MicrosoftWindows Server 2022 23H2< 10.0.25398.2092
MicrosoftWindows Server 2025< 10.0.26100.32230

Related Weaknesses (CWE)

CWE-1329

References

FAQ

What is CVE-2026-21265?

CVE-2026-21265 is a vulnerability with a CVSS score of 6.4 (MEDIUM). 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 ...

How severe is CVE-2026-21265?

CVE-2026-21265 has been rated MEDIUM with a CVSS base score of 6.4/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-21265?

Check the references section above for vendor advisories and patch information. Affected products include: Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21H2, Microsoft Windows 10 22H2, Microsoft Windows 11 23H2.