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CVE-2026-21265

MEDIUM CVSS 3.1: 6.4 EPSS 0.28%
Updated Jan 14, 2026
Microsoft
Parameter Value
CVSS 6.4 (MEDIUM)
Affected Versions before 10.0.26200.7623
Fixed In 10.0.14393.8783
Type CWE-1329
Vendor Microsoft
Public PoC No

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.

Attack Parameters

Attack Vector
Local
Requires local access
Attack Complexity
High
Difficult to exploit
Privileges Required
High
Admin privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service

CVSS Vector v3.1

Weakness Type (CWE)

Vulnerable Products 23

Configuration From (including) Up to (excluding)
Microsoft Windows_10_1607
cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*
10.0.14393.8783
Microsoft Windows_10_1607
cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*
10.0.14393.8783
Microsoft Windows_10_1809
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*
10.0.17763.8276
Microsoft Windows_10_1809
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*
10.0.17763.8276
Microsoft Windows_10_21h2
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:arm64:*
10.0.19044.6809
Microsoft Windows_10_21h2
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x64:*
10.0.19044.6809
Microsoft Windows_10_21h2
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x86:*
10.0.19044.6809
Microsoft Windows_10_22h2
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:arm64:*
10.0.19045.6809
Microsoft Windows_10_22h2
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x64:*
10.0.19045.6809
Microsoft Windows_10_22h2
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x86:*
10.0.19045.6809
Microsoft Windows_11_23h2
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:arm64:*
10.0.22631.6491
Microsoft Windows_11_23h2
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:x64:*
10.0.22631.6491
Microsoft Windows_11_24h2
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*
10.0.26100.7623
Microsoft Windows_11_24h2
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*
10.0.26100.7623
Microsoft Windows_11_25h2
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*
10.0.26200.7623
Microsoft Windows_11_25h2
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*
10.0.26200.7623
Microsoft Windows_Server_2012
cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
Microsoft Windows_Server_2012
cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
Microsoft Windows_Server_2016
cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*
10.0.14393.8783
Microsoft Windows_Server_2019
cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*
10.0.17763.8276
Microsoft Windows_Server_2022
cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
10.0.20348.4648
Microsoft Windows_Server_2022_23h2
cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*
10.0.25398.2092
Microsoft Windows_Server_2025
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*
10.0.26100.32230