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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.

PUBLISHED Reserved 2025-12-11 | Published 2026-01-13 | Updated 2026-02-22 | Assigner microsoft




MEDIUM: 6.4CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Problem types

CWE-1329 - Reliance on Component That is Not Updateable

Product status

10.0.14393.0 (custom) before 10.0.14393.8783
affected

10.0.17763.0 (custom) before 10.0.17763.8276
affected

10.0.19044.0 (custom) before 10.0.19044.6809
affected

10.0.19045.0 (custom) before 10.0.19045.6809
affected

10.0.22631.0 (custom) before 10.0.22631.6491
affected

10.0.22631.0 (custom) before 10.0.22631.6491
affected

10.0.26100.0 (custom) before 10.0.26100.7623
affected

10.0.26200.0 (custom) before 10.0.26200.7623
affected

6.2.9200.0 (custom) before 6.2.9200.25868
affected

6.2.9200.0 (custom) before 6.2.9200.25868
affected

6.3.9600.0 (custom) before 6.3.9600.22968
affected

6.3.9600.0 (custom) before 6.3.9600.22968
affected

10.0.14393.0 (custom) before 10.0.14393.8783
affected

10.0.14393.0 (custom) before 10.0.14393.8783
affected

10.0.17763.0 (custom) before 10.0.17763.8276
affected

10.0.17763.0 (custom) before 10.0.17763.8276
affected

10.0.20348.0 (custom) before 10.0.20348.4648
affected

10.0.25398.0 (custom) before 10.0.25398.2092
affected

10.0.26100.0 (custom) before 10.0.26100.32230
affected

10.0.26100.0 (custom) before 10.0.26100.32230
affected

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21265 (Secure Boot Certificate Expiration Security Feature Bypass Vulnerability) vendor-advisory patch

cve.org (CVE-2026-21265)

nvd.nist.gov (CVE-2026-21265)

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