CVE-2026-21265
6.4 · MEDIUMOverview
CVE-2026-21265 is a medium-severity vulnerability affecting microsoft windows_10_1607. It was published on January 13, 2026 and has a CVSS 3.1 base score of 6.4 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 6.4, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.
Technical 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
Remediation
Check the references section for vendor advisories and patches from microsoft. Update windows_10_1607 to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| microsoft | windows_10_1607 | >= 0, < 10.0.14393.8783 | Affected |
| microsoft | windows_10_1809 | >= 0, < 10.0.17763.8276 | Affected |
| microsoft | windows_10_21h2 | >= 0, < 10.0.19044.6809 | Affected |
| microsoft | windows_10_22h2 | >= 0, < 10.0.19045.6809 | Affected |
| microsoft | windows_11_23h2 | >= 0, < 10.0.22631.6491 | Affected |
| microsoft | windows_11_24h2 | >= 0, < 10.0.26100.7623 | Affected |
| microsoft | windows_11_25h2 | >= 0, < 10.0.26200.7623 | Affected |
| microsoft | windows_server_2016 | >= 0, < 10.0.14393.8783 | Affected |
| microsoft | windows_server_2019 | >= 0, < 10.0.17763.8276 | Affected |
| microsoft | windows_server_2022 | >= 0, < 10.0.20348.4648 | Affected |
| microsoft | windows_server_2022_23h2 | >= 0, < 10.0.25398.2092 | Affected |
| microsoft | windows_server_2025 | >= 0, < 10.0.26100.32230 | Affected |
Frequently Asked Questions
What is CVE-2026-21265?
CVE-2026-21265 is a medium-severity vulnerability affecting microsoft windows_10_1607. It was published on January 13, 2026 and has a CVSS 3.1 base score of 6.4 (MEDIUM).
How severe is CVE-2026-21265?
This vulnerability has a CVSS 3.1 base score of 6.4, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.
How do I fix or remediate CVE-2026-21265?
Check the references section for vendor advisories and patches from microsoft. Update windows_10_1607 to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-21265?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-21265 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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