A heap‑based buffer overflow exists within the Windows Client‑Side Caching (CSC) Service that permits an authorized user to elevate privileges locally. The flaw is a classic memory corruption issue (CWE‑122) that directly gains control of the service, which can be leveraged to increase the attacker’s privilege level on the host. This vulnerability offers no remote code execution path as stated in the description; it strictly implies local privilege escalation.

Microsoft Windows 10 versions 1607, 1809, 21H2 and 22H2; Windows 11 versions 23H2, 24H2, 25H2, 26H2 and 26H1; and Windows Server releases 2012, 2012 R2, 2016, 2019, 2022 and 2025, including their Server Core installations are all affected by this vulnerability.

The CVSS score of 7 indicates a high risk level. No EPSS score is reported and the vulnerability is not listed in CISA’s KEV catalog, suggesting limited publicly known exploitation. The attack vector inferred from the description is local: an attacker must first obtain authorized access to a host in order to exploit the CSC service. Once the heap overflow is triggered, the attacker can gain elevated privileges, potentially leading to full system compromise if the newly obtained privileges are administrative. The overall risk remains significant for environments where Client‑Side Caching is enabled and user privilege boundaries are not strictly enforced.