This vulnerability involves a heap-based buffer overflow in the Windows Kernel component of Windows 10 Version 1607 (build 10.0.14393.0). It enables a local attacker with authorized access to escalate privileges, potentially gaining higher system rights. The CVSS 3.1 vector indicates low attack complexity and low privileges required, with no user interaction needed. Microsoft has published an official fix to remediate this vulnerability.

Successful exploitation could allow an authorized local attacker to elevate their privileges, resulting in full control over the affected system. Confidentiality, integrity, and availability impacts are all rated high according to the CVSS vector. No public exploits have been reported so far.

An official patch is available from Microsoft to address this vulnerability. Users and administrators should apply the update provided in the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21239 to remediate the issue. Since this is a local privilege escalation vulnerability, applying the patch is the primary mitigation.