CVE-2026-21265 — Secure Boot Certificate Expiration Security Feature Bypass Vulnerability

Executive Summary

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. For more information see this CVE and Windows Secure Boot certificate expiration and CA updates .

Overview

6.4

CVSS MEDIUM

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Security Feature Bypass

Released Jan 13 2026

Last Updated Jan 13 2026

Publicly Disclosed Yes

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00965 — 0.57038 percentile

NVD CVSS 6.4 MEDIUM — matches MSRC

CVSS Vector

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

ATTACK VECTOR

Local

ATTACK COMPLEXITY

High

PRIVILEGES REQUIRED

High

USER INTERACTION

None

SCOPE

Unchanged

CONFIDENTIALITY

High

INTEGRITY

High

AVAILABILITY

High

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 5.6

EPSS Score

0.00965

probability of exploitation in the next 30 days

0.57038 percentile - updated 2026-06-21

View on FIRST.org

Affected Products

29 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 1607 for 32-bit Systems	`5073722 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 1607 for x64-based Systems	`5073722 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 1809 for 32-bit Systems	`5073723 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 1809 for x64-based Systems	`5073723 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5073724 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5073724 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 21H2 for x64-based Systems	`5073724 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5073724 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5073724 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 10 Version 22H2 for x64-based Systems	`5073724 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 11 Version 23H2 for ARM64-based Systems	`5073455 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 11 Version 23H2 for x64-based Systems	`5073455 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 11 Version 24H2 for ARM64-based Systems	`5074109 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 11 Version 24H2 for x64-based Systems	`5074109 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 11 Version 25H2 for ARM64-based Systems	`5074109 (Security Update)`	Important	Security Feature Bypass	Yes
Windows 11 Version 25H2 for x64-based Systems	`5074109 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2012	`5073698 (Monthly Rollup)`	Important	Security Feature Bypass	Yes
Windows Server 2012 (Server Core installation)	`5073698 (Monthly Rollup)`	Important	Security Feature Bypass	Yes
Windows Server 2012 R2	`5073696 (Monthly Rollup)`	Important	Security Feature Bypass	Yes
Windows Server 2012 R2 (Server Core installation)	`5073696 (Monthly Rollup)`	Important	Security Feature Bypass	Yes
Windows Server 2016	`5073722 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2016 (Server Core installation)	`5073722 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2019	`5073723 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2019 (Server Core installation)	`5073723 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2022	`5073457 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2022 (Server Core installation)	`5073457 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2022, 23H2 Edition (Server Core installation)	`5073450 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2025	`5073379 (Security Update)`	Important	Security Feature Bypass	Yes
Windows Server 2025 (Server Core installation)	`5073379 (Security Update)`	Important	Security Feature Bypass	Yes

Patches

10 patches

Article	Type	Restart
`5073722`	Security Update	Yes
`5073723`	Security Update	Yes
`5073724`	Security Update	Yes
`5073455`	Security Update	Yes
`5074109`	Security Update	Yes
`5073698`	Monthly Rollup	Yes
`5073696`	Monthly Rollup	Yes
`5073457`	Security Update	Yes
`5073450`	Security Update	Yes
`5073379`	Security Update	Yes

Known Exploits

No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.

Acknowledgments

Microsoft

References

MSRC Advisory MITRE NVD