The vulnerability is a heap‑based buffer overflow in Windows Client Side Caching driver (csc.sys) that allows an authorized attacker to elevate privileges locally. This flaw is a classic privilege escalation issue that can be exploited by users with local access to the affected systems.

Affected systems include Microsoft Windows 10 versions 1607, 1809, 21H2 and 22H2; Windows 11 versions 23H2, 24H2, 25H2, 22H3 and 26H1; and Windows Server releases 2012, 2012 R2, 2016, 2019, 2022, 2025 and the 23H2 edition. All of these versions run the csc.sys driver, which is impacted by the overflow.

The CVSS base score of 7.8 indicates high severity for a privilege escalation flaw. EPSS data is not available, so exploitation likelihood cannot be quantified, but the defect resides in a core system driver and may be triggered by a local attacker who can supply malformed data to the driver. The vulnerability is not currently listed in the CISA KEV catalog, and no publicly known exploits have been reported. The likely attack vector is local exploitation by an authenticated user or through crafted requests processed by csc.sys. Administrators should treat this as a high‑risk local attack scenario.