The vulnerability is an integer underflow condition in Windows PowerShell that allows an attacker, over a network, to execute arbitrary code on a target system. The underflow can cause the PowerShell engine to misinterpret data lengths or arithmetic values, leading to code execution with the privileges of the PowerShell process. The impact is the loss of confidentiality, integrity, and availability for any affected user account and potentially the entire system.

Affected systems include Microsoft Windows 10 versions 1607, 1809, 21H2, and 22H2; Microsoft Windows 11 versions 23H2, 24H2, 25H2, 26H2, 26H1; and Microsoft Windows Server versions 2012, 2012 R2, 2016, 2019, 2022, and 2025, including both standard and server core installations. The vulnerability affects both x86 and x64 architectures as well as ARM64 variants where applicable.

The CVSS score of 9.8 indicates critical severity, while the EPSS score is not available and the vulnerability is not listed in the CISA KEV catalog. The attack vector is remote over a network, implies that any network-accessible PowerShell service can be abused. The lack of an official patch in the provided data suggests that the vulnerability is mitigated by applying relevant Windows updates, so the risk remains high until the fix is installed.