The pages below shows you how to get information about the CU (Cumulative Update) for your SharePoint installation.
The first page shows you how to get information about the CU.
http://www.brightworksupport.com/find-your-sharepoint-cumulative-update-or-patch-level/
The second page shows you what CU you are using based on the information found through the first page.
http://blogs.technet.com/b/steve_chen/archive/2013/03/26/3561010.aspx