CVE-2026-21265 Secure Boot Certificate Expiration Security Feature Bypass Vulnerability

This post has been republished via RSS; it originally appeared at: MSRC Security Update Guide.

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](https://aka.ms/GetSecureBoot).