2016 CX5 has a rattle in the rear, it sounds like it is coming from inside the rear hatch, before I pull all the interior molding off are there any known culprits?

 

Without knowing exactly where it is coming from, you'll need to check a bunch of items to find out.
Rear differential, loose spoiler bolts, exhaust are some known rear rattle issues.
Use also could have some bad/loose parts in your lift gate mechanisms and/or wiper motor.
The lift supports could also be worn out and if worn enough they can rattle.
Even the trim and trim molding can come loose eventually.

 

Spoiler mounts are notoriously loosening themselves randomly. Also check the little triangular trim pieces just below the spoiler on the rear glass.

 

I second what Buzzard said.