yes the drive shaft bolts clamp the cover that seals the grease within the joint
-if you tighten the bolts up they may just come loose again due to grease contamination.
the fix is to undo the drive shaft, degrease the cup and especially the threads that the bolts go into.
I would have a really good look at the CV boots, if you can find any sign of wear and as your inner bolts are loose, you are only the hub nut/bolt away from removing the complete drive shaft allowing you to service the entire drive shaft with new boots & grease