Microsoft has released SQL Server 2014 Service Pack 2 Cumulative Update 4, which is Build 12.0.5540.0. There are 30 hotfixes in the public fix list. In my opinion, you should be on the SP2 branch by now. If you have not made that move, you should be making plans to get on SP2 as soon as possible.
They have also released SQL Server 2014 Service Pack 1 Cumulative Update 11, which is Build 12.0.4502.0. There are 15 hotfixes in the public fix list for this CU.
There is no corresponding CU for the RTM branch, since SQL Server 2014 RTM is no longer a supported Service Pack level.