CVE-2026-21265HighCVSS 6.4

Secure Boot Certificate Expiration Security Feature Bypass Vulnerability

Published
June 2, 2026
Last Modified
—

🔗 CVE IDs covered (1)

CVE-2026-21265 →

📋 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.

🎯 Affected products29

  • Windows 10 Version 1607 for 32-bit Systems
  • Windows 10 Version 1607 for x64-based Systems
  • Windows 10 Version 1809 for 32-bit Systems
  • Windows 10 Version 1809 for x64-based Systems
  • Windows 10 Version 21H2 for 32-bit Systems
  • Windows 10 Version 21H2 for ARM64-based Systems
  • Windows 10 Version 21H2 for x64-based Systems
  • Windows 10 Version 22H2 for 32-bit Systems
  • Windows 10 Version 22H2 for ARM64-based Systems
  • Windows 10 Version 22H2 for x64-based Systems
  • Windows 11 Version 23H2 for ARM64-based Systems
  • Windows 11 Version 23H2 for x64-based Systems
  • Windows 11 Version 24H2 for ARM64-based Systems
  • Windows 11 Version 24H2 for x64-based Systems
  • Windows 11 Version 25H2 for ARM64-based Systems
  • Windows 11 Version 25H2 for x64-based Systems
  • Windows Server 2012
  • Windows Server 2012 (Server Core installation)
  • Windows Server 2012 R2
  • Windows Server 2012 R2 (Server Core installation)
  • Windows Server 2016
  • Windows Server 2016 (Server Core installation)
  • Windows Server 2019
  • Windows Server 2019 (Server Core installation)
  • Windows Server 2022
  • Windows Server 2022 (Server Core installation)
  • Windows Server 2022, 23H2 Edition (Server Core installation)
  • Windows Server 2025
  • Windows Server 2025 (Server Core installation)

✅ Remediation

KB5073723 (Security Update) — fixed build 10.0.17763.8276 KB5073457 (Security Update) — fixed build 10.0.20348.4648 KB5073724 (Security Update) — fixed build 10.0.19044.6809 KB5073724 (Security Update) — fixed build 10.0.19045.6809 KB5073379 (Security Update) — fixed build 10.0.26100.32230 KB5074109 (Security Update) — fixed build 10.0.26200.7623 KB5073455 (Security Update) — fixed build 10.0.22631.6491 KB5073450 (Security Update) — fixed build 10.0.25398.2092 KB5074109 (Security Update) — fixed build 10.0.26100.7623 KB5073722 (Security Update) — fixed build 10.0.14393.8783 KB5073698 (Monthly Rollup) — fixed build 6.2.9200.25868 KB5073696 (Monthly Rollup) — fixed build 6.3.9600.22968

🔗 References (22)