The kernel in Microsoft Windows Server 2003 SP2, Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, and Windows 7 SP1 does not properly constrain impersonation levels, which allows local users to gain privileges via a crafted application, aka "Impersonation Level Check Elevation of Privilege Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-025