CVE-2026-21265: Secure Boot Certificate Expiration Security Feature Bypass Vulnerability
Microsoft · Windows 10 Version 1607
Vendor fix available · Affected: Microsoft Windows 10 Version 1607 · Exploitation: possible (1 to 10%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 66% of scored CVEs
DescriptionCVE.org
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 products20
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Microsoft · Windows 10 Version 1607from 10.0.14393.0 before 10.0.14393.8783
- Microsoft · Windows 10 Version 1809from 10.0.17763.0 before 10.0.17763.8276
- Microsoft · Windows 10 Version 21H2from 10.0.19044.0 before 10.0.19044.6809
- Microsoft · Windows 10 Version 22H2from 10.0.19045.0 before 10.0.19045.6809
- Microsoft · Windows 11 version 23H2from 10.0.22631.0 before 10.0.22631.6491
- Microsoft · Windows 11 Version 23H2from 10.0.22631.0 before 10.0.22631.6491
- Microsoft · Windows 11 Version 24H2from 10.0.26100.0 before 10.0.26100.7623
- Microsoft · Windows 11 Version 25H2from 10.0.26200.0 before 10.0.26200.7623
- Microsoft · Windows Server 2012from 6.2.9200.0 before 6.2.9200.25868
- Microsoft · Windows Server 2012 (Server Core installation)from 6.2.9200.0 before 6.2.9200.25868
- Microsoft · Windows Server 2012 R2from 6.3.9600.0 before 6.3.9600.22968
- Microsoft · Windows Server 2012 R2 (Server Core installation)from 6.3.9600.0 before 6.3.9600.22968
- Microsoft · Windows Server 2016from 10.0.14393.0 before 10.0.14393.8783
- Microsoft · Windows Server 2016 (Server Core installation)from 10.0.14393.0 before 10.0.14393.8783
- Microsoft · Windows Server 2019from 10.0.17763.0 before 10.0.17763.8276
- Microsoft · Windows Server 2019 (Server Core installation)from 10.0.17763.0 before 10.0.17763.8276
- Microsoft · Windows Server 2022from 10.0.20348.0 before 10.0.20348.4648
- Microsoft · Windows Server 2022, 23H2 Edition (Server Core installation)from 10.0.25398.0 before 10.0.25398.2092
- Microsoft · Windows Server 2025from 10.0.26100.0 before 10.0.26100.32230
- Microsoft · Windows Server 2025 (Server Core installation)from 10.0.26100.0 before 10.0.26100.32230
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Possible (1 to 10%). EPSS between 1% and 10%.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- Microsoft
- Published
- January 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-21265 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.