A heap-based buffer overflow in the Windows Win32 kernel subsystem allows an authorized attacker to elevate privileges locally. The flaw is triggered when the kernel processes untrusted input, resulting in a write beyond an allocated buffer; this can be leveraged to execute arbitrary code with SYSTEM-level privileges.

Microsoft Windows 10 versions 1607, 1809, 21H2, 22H2; Windows 11 versions 23H2, 24H2, 25H2, 26H2, 26H1; and Windows Server 2012 through 2025, including core installations.

The CVSS score of 7.8 denotes high severity, primarily due to local privilege escalation. No EPSS score is available, and the vulnerability is not listed in the CISA KEV catalog. Based on the description, the attack vector requires local authenticated access; the attacker must be able to run code on the affected system, enabling privilege escalation to SYSTEM level. Without the patch, an attacker could overwrite kernel memory and gain full administrative control.