CVE-2026-21265CWE-1329

CVE-2026-21265

Medium · published January 13, 2026

CVSS v3.1
6.4
EPSS
1%
Percentile
65.3
In the wild
Unconfirmed
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.

The record
Technical detail
CVSS v3.1
6.4 · MEDIUM
Vector
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.01096 · 65.3th percentile
Weakness
CWE-1329 · Reliance on Component That is Not Updateable
Published
2026-01-13T23:16Z
Affected products (23)
ProductVersionsFixed in
microsoft/windows_10_1607< 10.0.14393.878310.0.14393.8783
microsoft/windows_10_1607< 10.0.14393.878310.0.14393.8783
microsoft/windows_10_1809< 10.0.17763.827610.0.17763.8276
microsoft/windows_10_1809< 10.0.17763.827610.0.17763.8276
microsoft/windows_10_21h2< 10.0.19044.680910.0.19044.6809
microsoft/windows_10_21h2< 10.0.19044.680910.0.19044.6809
microsoft/windows_10_21h2< 10.0.19044.680910.0.19044.6809
microsoft/windows_10_22h2< 10.0.19045.680910.0.19045.6809
microsoft/windows_10_22h2< 10.0.19045.680910.0.19045.6809
microsoft/windows_10_22h2< 10.0.19045.680910.0.19045.6809
microsoft/windows_11_23h2< 10.0.22631.649110.0.22631.6491
microsoft/windows_11_23h2< 10.0.22631.649110.0.22631.6491
microsoft/windows_11_24h2< 10.0.26100.762310.0.26100.7623
microsoft/windows_11_24h2< 10.0.26100.762310.0.26100.7623
microsoft/windows_11_25h2< 10.0.26200.762310.0.26200.7623
microsoft/windows_11_25h2< 10.0.26200.762310.0.26200.7623
microsoft/windows_server_2012all versions—
microsoft/windows_server_2012all versions—
microsoft/windows_server_2016< 10.0.14393.878310.0.14393.8783
microsoft/windows_server_2019< 10.0.17763.827610.0.17763.8276
microsoft/windows_server_2022< 10.0.20348.464810.0.20348.4648
microsoft/windows_server_2022_23h2< 10.0.25398.209210.0.25398.2092
microsoft/windows_server_2025< 10.0.26100.3223010.0.26100.32230
References (1)
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21265 · [email protected]
EPSS history
Timeline
  • 13 JAN 17:56Z
    Secure Boot Certificate Expiration Security Feature Bypass Vulnerability
    cvelistv5