CVE-2026-69421: CWE-191: Integer Underflow (Wrap or Wraparound) in Microsoft Windows 10 Version 1607

This vulnerability involves an integer underflow (wrap or wraparound) in the Windows Kernel Mode Driver. An authorized local attacker can exploit this flaw to elevate privileges on affected Windows 10 versions. The issue is tracked as CWE-191. Multiple Windows 10 builds are affected, with versions ranging from 10.0.14393.0 up to but excluding various patched builds such as 10.0.14393.9512 and others. Microsoft has published an official fix for this vulnerability.

Successful exploitation allows a local attacker with authorized access to elevate their privileges, potentially gaining higher-level system permissions. This could lead to full system compromise depending on the attacker's goals and existing access.

An official fix is available from Microsoft. Users and administrators should apply the security updates provided by Microsoft for the affected Windows 10 versions as detailed in the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69421. No additional mitigation steps are indicated by the vendor.