CVE-2026-21265

mediumpriority · track · 0EPSS 0.011 · 65 %ileDEEUJPNLRUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

1.10% (65th) EPSS

CVSS 6.4 · medium

Is it mine?

181 products

Check your exposure

Who says so?

7 sources

cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-26

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.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedWindows 10 Version 1607 for 32-bit Systemsmsrc_csaf
10.0.14393.8783:Security Update:https://support.microsoft.com/help/5073722
https://support.microsoft.com/help/5073722
FixedWindows 10 Version 1607 for x64-based Systemsmsrc_csaf
10.0.14393.8783:Security Update:https://support.microsoft.com/help/5073722
https://support.microsoft.com/help/5073722
FixedWindows 10 Version 1809 for 32-bit Systemsmsrc_csaf
10.0.17763.8276:Security Update:https://support.microsoft.com/help/5073723
https://support.microsoft.com/help/5073723
FixedWindows 10 Version 1809 for x64-based Systemsmsrc_csaf
10.0.17763.8276:Security Update:https://support.microsoft.com/help/5073723
https://support.microsoft.com/help/5073723
FixedWindows 10 Version 21H2 for 32-bit Systemsmsrc_csaf
10.0.19044.6809:Security Update:https://support.microsoft.com/help/5073724
https://support.microsoft.com/help/5073724
FixedWindows 10 Version 21H2 for ARM64-based Systemsmsrc_csaf
10.0.19044.6809:Security Update:https://support.microsoft.com/help/5073724
https://support.microsoft.com/help/5073724
FixedWindows 10 Version 21H2 for x64-based Systemsmsrc_csaf
10.0.19044.6809:Security Update:https://support.microsoft.com/help/5073724
https://support.microsoft.com/help/5073724
FixedWindows 10 Version 22H2 for 32-bit Systemsmsrc_csaf
10.0.19045.6809:Security Update:https://support.microsoft.com/help/5073724
https://support.microsoft.com/help/5073724
FixedWindows 10 Version 22H2 for ARM64-based Systemsmsrc_csaf
10.0.19045.6809:Security Update:https://support.microsoft.com/help/5073724
https://support.microsoft.com/help/5073724
FixedWindows 10 Version 22H2 for x64-based Systemsmsrc_csaf
10.0.19045.6809:Security Update:https://support.microsoft.com/help/5073724
https://support.microsoft.com/help/5073724
FixedWindows 11 Version 23H2 for ARM64-based Systemsmsrc_csaf
10.0.22631.6491:Security Update:https://support.microsoft.com/help/5073455
https://support.microsoft.com/help/5073455
FixedWindows 11 Version 23H2 for x64-based Systemsmsrc_csaf
10.0.22631.6491:Security Update:https://support.microsoft.com/help/5073455
https://support.microsoft.com/help/5073455
FixedWindows 11 Version 24H2 for ARM64-based Systemsmsrc_csaf
10.0.26100.7623:Security Update:https://support.microsoft.com/help/5074109
https://support.microsoft.com/help/5074109
FixedWindows 11 Version 24H2 for x64-based Systemsmsrc_csaf
10.0.26100.7623:Security Update:https://support.microsoft.com/help/5074109
https://support.microsoft.com/help/5074109
FixedWindows 11 Version 25H2 for ARM64-based Systemsmsrc_csaf
10.0.26200.7623:Security Update:https://support.microsoft.com/help/5074109
https://support.microsoft.com/help/5074109
FixedWindows 11 Version 25H2 for x64-based Systemsmsrc_csaf
10.0.26200.7623:Security Update:https://support.microsoft.com/help/5074109
https://support.microsoft.com/help/5074109
FixedWindows Server 2012msrc_csaf
6.2.9200.25868:Monthly Rollup:https://support.microsoft.com/help/5073698
https://support.microsoft.com/help/5073698
FixedWindows Server 2012 (Server Core installation)msrc_csaf
6.2.9200.25868:Monthly Rollup:https://support.microsoft.com/help/5073698
https://support.microsoft.com/help/5073698
FixedWindows Server 2012 R2msrc_csaf
6.3.9600.22968:Monthly Rollup:https://support.microsoft.com/help/5073696
https://support.microsoft.com/help/5073696
FixedWindows Server 2012 R2 (Server Core installation)msrc_csaf
6.3.9600.22968:Monthly Rollup:https://support.microsoft.com/help/5073696
https://support.microsoft.com/help/5073696
FixedWindows Server 2016msrc_csaf
10.0.14393.8783:Security Update:https://support.microsoft.com/help/5073722
https://support.microsoft.com/help/5073722
FixedWindows Server 2016 (Server Core installation)msrc_csaf
10.0.14393.8783:Security Update:https://support.microsoft.com/help/5073722
https://support.microsoft.com/help/5073722
FixedWindows Server 2019msrc_csaf
10.0.17763.8276:Security Update:https://support.microsoft.com/help/5073723
https://support.microsoft.com/help/5073723
FixedWindows Server 2019 (Server Core installation)msrc_csaf
10.0.17763.8276:Security Update:https://support.microsoft.com/help/5073723
https://support.microsoft.com/help/5073723
FixedWindows Server 2022msrc_csaf
10.0.20348.4648:Security Update:https://support.microsoft.com/help/5073457
https://support.microsoft.com/help/5073457
FixedWindows Server 2022 (Server Core installation)msrc_csaf
10.0.20348.4648:Security Update:https://support.microsoft.com/help/5073457
https://support.microsoft.com/help/5073457
FixedWindows Server 2022, 23H2 Edition (Server Core installation)msrc_csaf
10.0.25398.2092:Security Update:https://support.microsoft.com/help/5073450
https://support.microsoft.com/help/5073450
FixedWindows Server 2025msrc_csaf
10.0.26100.32230:Security Update:https://support.microsoft.com/en-us/topic/a6021fd2-b3b7-45a7-b68e-35c28a2a77da
https://support.microsoft.com/en-us/topic/a6021fd2-b3b7-45a7-b68e-35c28a2a77da
FixedWindows Server 2025 (Server Core installation)msrc_csaf
10.0.26100.32230:Security Update:https://support.microsoft.com/en-us/topic/a6021fd2-b3b7-45a7-b68e-35c28a2a77da
https://support.microsoft.com/en-us/topic/a6021fd2-b3b7-45a7-b68e-35c28a2a77da

cvss

Technical severity, 0–10. One row per scoring source.

6.4

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.16.4mediumAV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.16.4mediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · ENISA EU

v3.16.4mediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:Hsecondary · secure@microsoft.com USexploitability 0.5 · impact 5.9

v3.15.9mediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

v3.16.4mediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · NCSC-NL NL

v3.16.4mediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · Microsoft Security Response Center US

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: no · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-1329USCWE-1329USCWE-1329US

affected products (181)

Products and version ranges known to be affected.

Hitachi Storageall versionscert_bundDEcpe:/h:hitachi:storage:-
Microsoft Windows 10 Version 1607all versionscert_bundDEcpe:/o:microsoft:windows_10:version_1607
Microsoft Windows 10 Version 1809all versionscert_bundDEcpe:/o:microsoft:windows_10:version_1809
Microsoft Windows 10 Version 21H2all versionscert_bundDEcpe:/o:microsoft:windows_10:version_21h2
Microsoft Windows 10 Version 22H2all versionscert_bundDEcpe:/o:microsoft:windows_10:version_22h2
Microsoft Windows 11 Version 23H2all versionscert_bundDEcpe:/o:microsoft:windows_11:version_23h2
Microsoft Windows 11 Version 24H2all versionscert_bundDEcpe:/o:microsoft:windows_11:version_24h2
Microsoft Windows 11 Windows Terminalall versionscert_bundDEcpe:/o:microsoft:windows_11:windows_terminal
Microsoft Windows Server 2008 R2 SP1all versionscert_bundDEcpe:/o:microsoft:windows_server:2008_r2_sp1
Microsoft Windows Server 2008 SP2all versionscert_bundDEcpe:/o:microsoft:windows_server:2008_sp2
Microsoft Windows Server 2012all versionscert_bundDEcpe:/o:microsoft:windows_server_2012:-
Microsoft Windows Server 2012 R2all versionscert_bundDEcpe:/o:microsoft:windows_server_2012_r2:-
Microsoft Windows Server 2016all versionscert_bundDEcpe:/o:microsoft:windows_server_2016:-
Microsoft Windows Server 2019all versionscert_bundDEcpe:/o:microsoft:windows_server_2019:-
Microsoft Windows Server 2022all versionscert_bundDEcpe:/o:microsoft:windows_server_2022:-
Microsoft Windows Server 2022 23H2 Editionall versionscert_bundDEcpe:/o:microsoft:windows_server_2022:23h2_edition
Microsoft Windows Server 2025all versionscert_bundDEcpe:/o:microsoft:windows_server_2025:-
Microsoft Windows 10 Version 160710.0.14393.0 → 10.0.14393.8783enisa_euvdEU
Microsoft Windows 10 Version 180910.0.17763.0 → 10.0.17763.8276enisa_euvdEU
Microsoft Windows 10 Version 21H210.0.19044.0 → 10.0.19044.6809enisa_euvdEU

showing 20 of 181

advisories (4)

Vendor and ecosystem advisories describing this.

NCSC-2026-0007Kwetsbaarheden verholpen in Microsoft WindowsNL2026-01-13csaf · ncsc_nlNL
Microsoft heeft kwetsbaarheden verholpen in Windows
WID-SEC-W-2026-0083Microsoft Windows : Mehrere SchwachstellenDeutsch2026-01-13csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in verschiedenen Versionen von Microsoft Windows und Microsoft Windows Server ausnutzen,, um erweiterte Privilegien, einschließlich Benutzer- und Administratorrechten, zu erlangen, beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen, einen Denial-of-Service-Zustand zu verursachen und Daten zu manipulieren.
msrc_CVE-2026-21265Secure Boot Certificate Expiration Security Feature Bypass Vulnerability2026-01-13csaf · msrc_csafUS
To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle
JVNDB-2026-004359JVN iPedia advisory JVNDB-2026-0043592026-02-20vendor · jvndbJP

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cert_bund ncsc_nl msrc_csaf jvndb NVD CVE.org MITRE

published 2026-01-13modified 2026-07-30

references (3)

External citations — patches, advisories, analysis.

scry

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