Macbook retina 2012: CPU temperature too high
There are two likely issues afoot here:


Your System Management Controller has gotten some corruption.
You're seeing potential hardware-/sensor failures.


To reset your SMC, follow these instructions: http://support.apple.com/kb/HT3964

If that doesn't solve the problem, I'd run Apple Diagnostics and see whether it picks up on any hardware problems. If it does, the system should be taken to Apple or an Apple-authorized repair centre for further testing and repair.