A heap-based buffer overflow exists in the Windows Win32 Kernel Subsystem (Win32k) that allows an attacker who already has authorized local access to overwrite memory and elevate privileges. The flaw stems from unchecked input handling within the kernel, giving the attacker the ability to execute code with higher privileges than their current user account. The primary impact is the gain of administrative rights or other elevated privileges, enabling further compromise of the system.

Microsoft Windows 10 releases 1607, 1809, 21H2, and 22H2; Microsoft Windows 11 releases 23H2, 24H2, 25H2, 26H2, and 26H1; Microsoft Windows Server 2016, Server 2016 Core, Windows Server 2019, Server 2019 Core, Windows Server 2022, and Windows Server 2025 (including Server 2025 Core).

The CVSS score of 7.8 indicates moderate to high severity, while the EPSS score is not currently available. The vulnerability is not listed in the CISA KEV catalog. Based on the description, the likely attack vector is local, requiring the attacker to have legitimate user access to the target machine. Exploitation requires triggering a heap overflow within the kernel, which is typically achievable via crafted input from a privileged user process. Given these factors, the risk is moderate but escalation to higher privileges remains a significant threat.