An elevation of privilege vulnerability exists in Microsoft Windows when it fails to properly validate and enforce impersonation levels. 
An attacker who successfully exploited this vulnerability could bypass impersonation-level security checks and gain elevated privileges on a targeted system. 
This vulnerability can be exploited only in the specific scenario where the process uses SeAssignPrimaryTokenPrivilege, which is not available for normal processes.

c:\> MS15-015.exe "whoami"