Improper authentication in Windows SMB Server allows an authorized attacker to bypass authentication checks and elevate privileges locally. The flaw is an authentication bypass (CWE‑287) and can enable the attacker to gain administrative rights, install software, exfiltrate data, or alter system configurations, effectively granting full control over the affected machine.

The vulnerability affects Microsoft Windows 10 versions 1607, 1809, 21H2, and 22H2, as well as Windows 11 versions 22H3, 23H2, 24H2, 25H2, and 26H1. It also applies to Windows Server releases 2012, 2012 R2, 2016, 2019, 2022, 2025, and the 23H2 edition of Windows Server, covering both core and non‑core installations.

The CVSS score of 7.8 indicates high severity, but the EPSS score of less than 1% suggests a low likelihood of exploitation in the wild. The vulnerability is not listed in the CISA KEV catalog. The attack vector is inferred to be via SMB from a local, authenticated user; significant risk materializes when an attacker can access the network segment that hosts the vulnerable system.