Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · unedited
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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidence
Windows Secure Boot certificates (KEK CA 2011, UEFI CA 2011, Windows Production PCA 2011) stored in UEFI variables are approaching expiration dates in 2026. The firmware-based certificate update mechanism may contain defects that can cause trust updates to fail or behave unpredictably, potentially disrupting the Secure Boot trust chain and leading to security degradation or boot failures.
MitigationUpdate UEFI firmware and apply Microsoft certificate updates before expiration dates; validate that the certificate update mechanism functions correctly and does not introduce instability in the Secure Boot trust chain.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Windows 10 1607Operating system
Affected:< 10.0.14393.8783
Windows 10 1809Operating system
Affected:< 10.0.17763.8276
Windows 10 21h2Operating system
Affected:< 10.0.19044.6809
Windows 10 22h2Operating system
Affected:< 10.0.19045.6809
Windows 11 23h2Operating system
Affected:< 10.0.22631.6491
Windows 11 24h2Operating system
Affected:< 10.0.26100.7623
Windows 11 25h2Operating system
Affected:< 10.0.26200.7623
Windows Server 2012Operating system
Affected:all versions= r2
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector
Attack vector
Local
Complexity
High
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checks
Work through these to decide whether this CVE applies to you.
Verify Secure Boot status is enabled
Open PowerShell as Administrator and run: 'Confirm-SecureBootUEFI'. If it returns True, Secure Boot is enabled.
Affected if Secure Boot is disabled - the vulnerability only affects systems with Secure Boot enabled and using the affected certificate update mechanism
Query UEFI certificates for expiration dates
Run 'Get-SecureBootCertificate -CertificateKEK' and similar commands for UEFI CA 2011 and Windows Production PCA 2011, or use 'certutil -dump' on UEFI variables via elevated command prompt to view certificate details including NotAfter dates.
Affected if Any of the three certificates (KEK CA 2011, UEFI CA 2011, Windows Production PCA 2011) show expiration dates in 2026 or earlier and have not been updated
Check for certificate update status
Examine UEFI variable 'db' (database) using 'certutil -dump' or PowerShell to see if newer replacement certificates have been installed versus the original 2011 certificates.
Affected if The system is still using the original 2011 certificates without updated replacements present in UEFI variables
Check Windows version against affected ranges
Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' and compare the build number to the affected version list: 14393.8783, 17763.8276, 19044.6809, 19045.6809, 22631.6491, 26100.7623, 26200.7623. Also check Windows Server 2012/2012 R2.
Affected if Running an affected Windows version or Windows Server 2012/2012 R2 with Secure Boot enabled and unpatched certificates
You are affected if Secure Boot is enabled, you run an unpatched Windows version from the affected list, and the UEFI certificates have not been updated past the 2011 originals with expiration approaching 2026.
Generated from the published advisory. Verify against your own configuration.
Check your environment
Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.
AI-assisted, checked against the advisory. Informational, not a guarantee.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped
Upgrade availableUpgrade to 10.0.14393.8783 / 10.0.17763.8276 / 10.0.19044.6809 or later
Update UEFI firmware and apply Microsoft certificate updates before expiration dates; validate that the certificate update mechanism functions correctly and does not introduce instability in the Secure Boot trust chain.
Recommended fixHigh confidence
Windows 10 1607 build 10.0.14393.8783 or later | Windows 10 1809 build 10.0.17763.8276 or later | Windows 10 21h2 build 10.0.19044.6809 or later | Windows 10 22h2 build 10.0.19045.6809 or later | Windows 11 23h2 build 10.0.22631.6491 or later | Windows 11 24h2 build 10.0.26100.7623 or later | Window
Open Windows Settings and navigate to Windows Update
Click 'Check for updates' and install all available updates
Restart the system after updates are installed
Verify Secure Boot is enabled by running 'systeminfo' in Command Prompt and checking the 'Secure Boot State' value
Ensure the system has the latest UEFI/firmware updates from the hardware vendor
Caveat Users with disabled Automatic Updates must manually install the certificate update patches; systems with custom firmware may need additional vendor-specific updates
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Windows 10 1607
Scoped from the published advisory
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,288.
Scan for this in your stack
Free · runs locally
dbcve dependency scanner
Check whether your project pulls in CVE-2026-21265 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Agent discussion
published at 80%7 agents10 Aug 2026
CVE-2026-21265 is being characterized as a certificate expiration issue, but the real vulnerability is the dependency on heterogeneous firmware to deliver those certificate updates — firmware you cannot audit, cannot force-patch, and cannot verify has succeeded without specialized tooling.
Three certificates in the Secure Boot trust chain expire in 2026: the KEK CA on June 24, the UEFI CA on June 27, and a third certificate on October 19. The critical detail is that updating these certificates depends on firmware update mechanisms that vary across every OEM — Dell, HP, Lenovo, and dozens of smaller vendors each implement the KEK/DB update pathway differently. Microsoft's CVE acknowledges these updates can "fail or behave unpredictably," and that word "unpredictably" should concern you more than the expiration dates themselves.
Here's why: if the KEK CA update fails, you lose more than one certificate. The KEK (Key Exchange Key) is the signing authority for all subsequent DB and DBX updates. A failed or partially-corrupted KEK update doesn't just leave a system unpatched — it breaks the entire certificate update channel. Systems could become permanently unbootable, particularly those with third-party bootloaders signed only under the 2011 UEFI CA, from vendors who may no longer exist or never implemented the renewal pathway.
What you should do now: First, inventory your firmware versions across the fleet — most endpoint management tools don't expose UEFI KEK/DB certificate states, so you may need vendor-specific tooling (Dell Command | Configure, HP BIOS Configuration Utility, Lenovo System Update) or HWInfo-style sensors to read certificate validity dates directly from the UEFI variables. Second, prioritize the June expirations: the KEK CA is your critical path because its failure cascades to all subsequent updates. Third, test your firmware update mechanism on representative hardware from each OEM in your environment before the deadline — don't assume the update will succeed just because the hardware boots.
The CVSS 6.4 medium rating reflects the intended fix (successful firmware update restores security), not the failure state. The failure taxonomy — what actually happens when these updates go wrong across the OEM ecosystem — is not documented in the CVE. Treat this as a critical-severity operational risk with medium exploitability, not a medium-severity issue.
Peer-ranked notes from engineers who’ve handled CVE-2026-21265 in production — separate from our analysis above.
Know something about CVE-2026-21265?
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon
▲0
Secure Boot Trust Paneldbcve analysis2026-08-10
CVE-2026-21265 is being characterized as a certificate expiration issue, but the real vulnerability is the dependency on heterogeneous firmware to deliver those certificate updates — firmware you cannot audit, cannot force-patch, and cannot verify has succeeded without specialized tooling.
Three certificates in the Secure Boot trust chain expire in 2026: the KEK CA on June 24, the UEFI CA on June 27, and a third certificate on October 19. The critical detail is that updating these certificates depends on firmware update mechanisms that vary across every OEM — Dell, HP, Lenovo, and dozens of smaller vendors each implement the KEK/DB update pathway differently. Microsoft's CVE acknowledges these updates can "fail or behave unpredictably," and that word "unpredictably" should concern you more than the expiration dates themselves.
Here's why: if the KEK CA update fails, you lose more than one certificate. The KEK (Key Exchange Key) is the signing authority for all subsequent DB and DBX updates. A failed or partially-corrupted KEK update doesn't just leave a system unpatched — it breaks the entire certificate update channel. Systems could become permanently unbootable, particularly those with third-party bootloaders signed only under the 2011 UEFI CA, from vendors who may no longer exist or never implemented the renewal pathway.
What you should do now: First, inventory your firmware versions across the fleet — most endpoint management tools don't expose UEFI KEK/DB certificate states, so you may need vendor-specific tooling (Dell Command | Configure, HP BIOS Configuration Utility, Lenovo System Update) or HWInfo-style sensors to read certificate validity dates directly from the UEFI variables. Second, prioritize the June expirations: the KEK CA is your critical path because its failure cascades to all subsequent updates. Third, test your firmware update mechanism on representative hardware from each OEM in your environment before the deadline — don't assume the update will succeed just because the hardware boots.
The CVSS 6.4 medium rating reflects the intended fix (successful firmware update restores security), not the failure state. The failure taxonomy — what actually happens when these updates go wrong across the OEM ecosystem — is not documented in the CVE. Treat this as a critical-severity operational risk with medium exploitability, not a medium-severity issue.
What this is
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