CVE-2026-21265: Microsoft Windows 10 Version 1607 · - Reliance on Component That is Not Updateable
Affects Microsoft Windows 10 Version 1607Source CVE Database V5
Not known to be exploited · CVSS 6.4 Medium : upgrade to 10.0.14393.8783 when convenient.
Data as of 26 Oct 2026, 06:26 UTC
- EPSS
- 1.0% chance of exploitation in 30 days – higher than 65% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 10.0.14393.8783, 10.0.17763.8276, 10.0.19044.6809 +9
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CExploitation evidence
Disclosed: evidence found.
CVE published 13 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| MicrosoftWindows 10 Version 1607 | Affected
| Fixed in
|
| MicrosoftWindows 10 Version 1809 | Affected
| Fixed in
|
| MicrosoftWindows 10 Version 21H2 | Affected
| Fixed in
|
| MicrosoftWindows 10 Version 22H2 | Affected
| Fixed in
|
| MicrosoftWindows 11 version 23H2 | Affected
| Fixed in
|
| MicrosoftWindows 11 Version 23H2 | Affected
| Fixed in
|
| MicrosoftWindows 11 Version 24H2 | Affected
| Fixed in
|
| MicrosoftWindows 11 Version 25H2 | Affected
| Fixed in
|
| MicrosoftWindows Server 2012 | Affected
| Fixed in
|
| MicrosoftWindows Server 2012 (Server Core installation) | Affected
| Fixed in
|
| MicrosoftWindows Server 2012 R2 | Affected
| Fixed in
|
| MicrosoftWindows Server 2012 R2 (Server Core installation) | Affected
| Fixed in
|
| MicrosoftWindows Server 2016 | Affected
| Fixed in
|
| MicrosoftWindows Server 2016 (Server Core installation) | Affected
| Fixed in
|
| MicrosoftWindows Server 2019 | Affected
| Fixed in
|
| MicrosoftWindows Server 2019 (Server Core installation) | Affected
| Fixed in
|
| MicrosoftWindows Server 2022 | Affected
| Fixed in
|
| MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation) | Affected
| Fixed in
|
| MicrosoftWindows Server 2025 | Affected
| Fixed in
|
| MicrosoftWindows Server 2025 (Server Core installation) | Affected
| Fixed in
|
AI-suggested
An official fix is available from Microsoft to update the expiring Secure Boot certificates. Administrators should apply the provided security updates as directed in the Microsoft advisory (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21265) to ensure Secure Boot functionality is maintained and security guarantees are restored. Careful validation and deployment of these updates are necessary due to potential firmware-related update issues.
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.