What is the severity of CVE-2026-21265?

CVE-2026-21265 has a CVSS v3 score of 6.4, which is classified as Medium severity.

Is there an exploit available for CVE-2026-21265?

No known public exploits are currently available for CVE-2026-21265.

Is there a patch available for CVE-2026-21265?

Yes, patches are available for CVE-2026-21265. Check the vendor advisories for update instructions.

CVE-2026-21265 - CVE Details, Severity, and Analysis

Published: January 29, 2026

Last updated:1 hour ago (January 29, 2026)

Updated January 29, 2026

no major risk factors

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.

Strobes VI. (2026). CVE-2026-21265 - CVE Details and Analysis. Strobes VI. Retrieved January 29, 2026, from https://vi.strobes.co/cve/CVE-2026-21265

Vendor	Product
Microsoft	Windows Server 2012
Microsoft

NVD: 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.