When a user connects to a Remote Desktop Server (RDS) by using a Smart Card, and then disconnects from the session but the user session stays logged on, the Scenumdevice.exe, Certprop.exe and Scardsrv.exe processes consume 100 percent of CPU resources on a single processor core.
This is a known issue with Windows Server 2012 R2.
To resolve this issue, install the December 2014 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
See the terminology that Microsoft uses to describe software updates.