CVE-2026-21265
Medium CVSS 6.4Published 2026-01-13 · last changed 2026-07-30
The fix
Microsoft fixes this in updatesKB5073722, KB5073723, KB5073724, KB5073455, KB5074109, KB5073698, KB5073696, KB5073457, KB5073450, KB5073379. The fixed build differs per Windows version, so the row that matters is the one matching the machine you are looking at.
| Windows version | Fixed in build | Update | Released |
|---|---|---|---|
| Windows 10 Version 1607 for 32-bit Systems | 10.0.14393.8783 | KB5073722 | 2026-09-20 |
| Windows 10 Version 1607 for x64-based Systems | 10.0.14393.8783 | KB5073722 | 2026-09-20 |
| Windows 10 Version 1809 for 32-bit Systems | 10.0.17763.8276 | KB5073723 | 2026-09-20 |
| Windows 10 Version 1809 for x64-based Systems | 10.0.17763.8276 | KB5073723 | 2026-09-20 |
| Windows 10 Version 21H2 for 32-bit Systems | 10.0.19044.6809 | KB5073724 | 2026-09-20 |
| Windows 10 Version 21H2 for ARM64-based Systems | 10.0.19044.6809 | KB5073724 | 2026-09-20 |
| Windows 10 Version 21H2 for x64-based Systems | 10.0.19044.6809 | KB5073724 | 2026-09-20 |
| Windows 10 Version 22H2 for 32-bit Systems | 10.0.19045.6809 | KB5073724 | 2026-09-20 |
| Windows 10 Version 22H2 for ARM64-based Systems | 10.0.19045.6809 | KB5073724 | 2026-09-20 |
| Windows 10 Version 22H2 for x64-based Systems | 10.0.19045.6809 | KB5073724 | 2026-09-20 |
| Windows 11 Version 23H2 for ARM64-based Systems | 10.0.22631.6491 | KB5073455 | 2026-09-20 |
| Windows 11 Version 23H2 for x64-based Systems | 10.0.22631.6491 | KB5073455 | 2026-09-20 |
| Windows 11 Version 24H2 for ARM64-based Systems | 10.0.26100.7623 | KB5074109 | 2026-09-20 |
| Windows 11 Version 24H2 for x64-based Systems | 10.0.26100.7623 | KB5074109 | 2026-09-20 |
| Windows 11 Version 25H2 for ARM64-based Systems | 10.0.26200.7623 | KB5074109 | 2026-09-20 |
| Windows 11 Version 25H2 for x64-based Systems | 10.0.26200.7623 | KB5074109 | 2026-09-20 |
| Windows Server 2012 | 6.2.9200.25868 | KB5073698 | 2026-09-20 |
| Windows Server 2012 R2 | 6.3.9600.22968 | KB5073696 | 2026-09-20 |
| Windows Server 2012 R2 (Server Core installation) | 6.3.9600.22968 | KB5073696 | 2026-09-20 |
| Windows Server 2012 (Server Core installation) | 6.2.9200.25868 | KB5073698 | 2026-09-20 |
| Windows Server 2016 | 10.0.14393.8783 | KB5073722 | 2026-09-20 |
| Windows Server 2016 (Server Core installation) | 10.0.14393.8783 | KB5073722 | 2026-09-20 |
| Windows Server 2019 | 10.0.17763.8276 | KB5073723 | 2026-09-20 |
| Windows Server 2019 (Server Core installation) | 10.0.17763.8276 | KB5073723 | 2026-09-20 |
| Windows Server 2022 | 10.0.20348.4648 | KB5073457 | 2026-09-20 |
| Windows Server 2022, 23H2 Edition (Server Core installation) | 10.0.25398.2092 | KB5073450 | 2026-09-20 |
| Windows Server 2022 (Server Core installation) | 10.0.20348.4648 | KB5073457 | 2026-09-20 |
| Windows Server 2025 | 10.0.26100.32230 | KB5073379 | 2026-09-20 |
| Windows Server 2025 (Server Core installation) | 10.0.26100.32230 | KB5073379 | 2026-09-20 |
Having the KB is not the same as knowing whether a machine has it. Windows updates supersede each other, so the update you installed often covers a fix that shipped in an earlier one. Paste your build into the patch checker and it walks that chain for you.
What it is
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.
Sources
CVSS vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H