A heap‑based buffer overflow in the Windows kernel allows an attacker who already has local access to elevate privileges to system level. The flaw arises from unvalidated memory operations during heap allocation, enabling the attacker to execute arbitrary code with kernel or SYSTEM privileges. This results in full compromise of confidentiality, integrity, and availability of the affected machine.

Microsoft Windows 11 version 26H1, ARM64 builds as indicated by the CPE string, is affected. Any device running this build that has not applied the security update and has local authorized access is susceptible to exploitation.

The CVSS score of 7.8 indicates moderate‑to‑high severity. The EPSS score is not reported and the vulnerability is not listed in CISA’s KEV catalog, so the overall exploitation risk is uncertain but notable. The attack vector is local, requiring the attacker to already have some legitimate access to the system. If a user can obtain elevated privileges, they can gain full control of the machine. Prompt patching and strict privilege management are required to mitigate this risk.