As announced earlier, Microsoft released the CU8 cumulative update for Microsoft Dynamics AX 2012 R2 (KB3042171). The version number of this release is 6.2.2000.14. So there is a cumulative update 8 for both AX 2012 R2 and AX 2012 R3 available. Due to the differences between R2 and R3 also the cumulative update 8 has differences between these versions.
You can download the update from the Microsoft Support site.