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CVE

CVE-2026-21265

Windows Secure Boot stores Microsoft certificates in the UEFI KEK and DB. These original certificates are approaching ex

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.

MEDIUM · CVSS 6.4 EPSS 0.00809
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0

Weakness Classification

Affected Products & Versions

13
microsoft windows 10 1607< 10.0.14393.8783
microsoft windows 10 1809< 10.0.17763.8276
microsoft windows 10 21h2< 10.0.19044.6809
microsoft windows 10 22h2< 10.0.19045.6809
microsoft windows 11 23h2< 10.0.22631.6491
microsoft windows 11 24h2< 10.0.26100.7623
microsoft windows 11 25h2< 10.0.26200.7623

Scoring & Timeline

6.4
MEDIUM · CVSS v3.1 · secure@microsoft.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD13 Jan 2026 · 06:16 PM
CVSS VectorCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.

Vendor Advisories

1
msrcCVE-2026-21265Security Feature Bypass
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