CVE-2026-21265

EUVD-2026-2100

13.01.2026, 18:16

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.

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	Primary	6.4 MEDIUM	LOCAL	HIGH	HIGH	CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
microsoft	CNA	6.4 MEDIUM				CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Base Score

CVSS 3.x

EPSS Score

Percentile: 49%

Affected Products (NVD)

Vendor	Product	Version
microsoft	windows_10_1607	𝑥 < 10.0.14393.8783
microsoft	windows_10_1607	𝑥 < 10.0.14393.8783
microsoft	windows_10_1809	𝑥 < 10.0.17763.8276
microsoft	windows_10_1809	𝑥 < 10.0.17763.8276
microsoft	windows_10_21h2	𝑥 < 10.0.19044.6809
microsoft	windows_10_21h2	𝑥 < 10.0.19044.6809
microsoft	windows_10_21h2	𝑥 < 10.0.19044.6809
microsoft	windows_10_22h2	𝑥 < 10.0.19045.6809
microsoft	windows_10_22h2	𝑥 < 10.0.19045.6809
microsoft	windows_10_22h2	𝑥 < 10.0.19045.6809
microsoft	windows_11_23h2	𝑥 < 10.0.22631.6491
microsoft	windows_11_23h2	𝑥 < 10.0.22631.6491
microsoft	windows_11_24h2	𝑥 < 10.0.26100.7623
microsoft	windows_11_24h2	𝑥 < 10.0.26100.7623
microsoft	windows_11_25h2	𝑥 < 10.0.26200.7623
microsoft	windows_11_25h2	𝑥 < 10.0.26200.7623
microsoft	windows_server_2012	-
microsoft	windows_server_2016	𝑥 < 10.0.14393.8783
microsoft	windows_server_2019	𝑥 < 10.0.17763.8276
microsoft	windows_server_2022	𝑥 < 10.0.20348.4648
microsoft	windows_server_2022_23h2	𝑥 < 10.0.25398.2092
microsoft	windows_server_2025	𝑥 < 10.0.26100.32230

𝑥

= Vulnerable software versions

Windows Releases

Platform

Version

Windows 10

1607 (x64, x86)	KB5073722
1809 (x64, x86)	KB5073723
21H2 (arm64, x64, x86)	KB5073724
22H2 (arm64, x64, x86)	KB5073724

Windows 11

23H2 (arm64, x64)	KB5073455
24H2 (arm64, x64)	KB5074109
25H2 (arm64, x64)	KB5074109

Windows Server 2012

Server Core	KB5073698
Standard	KB5073698

Windows Server 2012 R2

Server Core	KB5073696
Standard	KB5073696

Windows Server 2016

Server Core	KB5073722
Standard	KB5073722

Windows Server 2019

Server Core	KB5073723
Standard	KB5073723

Windows Server 2022

23H2 Server Core	KB5073450
Server Core	KB5073457
Standard	KB5073457

Windows Server 2025

Server Core	KB5073379
Standard	KB5073379

Common Weakness Enumeration

CWE-1329 - Reliance on Component That is Not Updateable
The product contains a component that cannot be updated or patched in order to remove vulnerabilities or significant bugs.

Vulnerability Media Exposure

[ENGLISH] Microsoft Fixes Three Zero-Days on Busy Patch Tuesday
Microsoft has patched three zero-day vulnerabilities in the first patch Tuesday of 2026, including one under active exploitation
Published: 2026-01-14T10:45:00+00:00

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21265