Vulnerability in Microsoft Windows 10 1607
CVE-2026-21265
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.4 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.011 (65.1th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 65.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: +0.000
Affected products
- Microsoft Windows 10 1607
- Microsoft Windows 10 1809
- Microsoft Windows 10 21h2
- Microsoft Windows 10 22h2
- Microsoft Windows 10 Version 1607 — versions 10.0.14393.0
- Microsoft Windows 10 Version 1809 — versions 10.0.17763.0
- Microsoft Windows 10 Version 21h2 — versions 10.0.19044.0
- Microsoft Windows 10 Version 22h2 — versions 10.0.19045.0
- Microsoft Windows 11 23h2
- Microsoft Windows 11 24h2
Weakness classification (CWE)
References
- msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21265 (vendor-advisory, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-21265?
- CVE-2026-21265 is a medium-severity vulnerability in Microsoft Windows 10 1607, classified under CWE-1329. CVSS score: 6.4/10. Published 2026-01-13.
- How severe is CVE-2026-21265?
- Medium severity. CVSS v3 base score is 6.4 out of 10.