CVE-2026-21265

6.4

MEDIUM CVSS 3.1

Secure Boot Certificate Expiration Security Feature Bypass Vulnerability

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 Boot Manager 10/19/2026 For more information see this CVE and Windows Secure Boot certificate expiration and CA updates.

INFO

Published Date :

Jan. 13, 2026, 6:16 p.m.

Last Modified :

Jan. 14, 2026, 8:23 p.m.

Remotely Exploit :

No

Source :

[email protected]

Affected Products

The following products are affected by CVE-2026-21265 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID	Vendor	Product
1	Microsoft	windows_server_2012
2	Microsoft	windows_server_2016
3	Microsoft	windows_server_2019
4	Microsoft	windows_10_1607
5	Microsoft	windows_10_1809
6	Microsoft	windows_10_21h2
7	Microsoft	windows_10_22h2
8	Microsoft	windows_server_2022
9	Microsoft	windows_11_23h2
10	Microsoft	windows_server_2022_23h2
11	Microsoft	windows_server_23h2
12	Microsoft	windows_server_2012_r2
13	Microsoft	windows_11_24h2
14	Microsoft	windows_server_2025
15	Microsoft	windows_11_25h2

: Total Affected Vendor : 1 | Products : 15

CVSS Scores

The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.

Score	Version	Severity	Vector	Exploitability Score	Impact Score	Source
	CVSS 3.1	MEDIUM				f38d906d-7342-40ea-92c1-6c4a2c6478c8
	CVSS 3.1	MEDIUM				[email protected]

Solution

Update Windows Secure Boot certificates to maintain security and functionality.

Apply the relevant security updates.
Update UEFI KEK and DB certificates.
Restart affected systems after updates.

References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-21265.

URL	Resource
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21265	Vendor Advisory

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-21265 is associated with the following CWEs:

CWE-1329: Reliance on Component That is Not Updateable

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-21265 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-21265 vulnerability anywhere in the article.

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