This vulnerability concerns the reliance on non-updateable or defective firmware components in Windows 10 Version 1607's Secure Boot certificate update process. Microsoft certificates stored in the UEFI KEK and DB, which validate boot loaders and the Windows Boot Manager, are approaching expiration in 2026. If these certificates are not properly updated due to firmware defects, Secure Boot's trust chain can be broken, potentially allowing security fixes related to boot integrity to be bypassed or lost. The issue is tracked as CWE-1329 and has a CVSS 3.1 base score of 6.4 (medium severity). An official fix from Microsoft is available to update the certificates and maintain Secure Boot functionality.

If the certificates expire without successful updates, Secure Boot may fail to validate boot components, potentially allowing unauthorized code execution during system startup. This compromises the integrity and security of the boot process, impacting confidentiality, integrity, and availability of the system. The vulnerability requires high privileges and local access to exploit, and user interaction is not required. No known exploits are reported in the wild at this time.

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.