Cinder block repair uses a concrete bonder for adhesion, patching cement and some material to plug the holes for the cement block repair.
The usual cause is water has been seeping behind the paint on your block wall for some time. It would seem the oil-based paint that was previously applied to the wall retained moisture causing the cinder blocks to break down. A water-based paint would have permitted the moisture to evaporate away. You need patching cement to repair these holes.
Your first job is to remove all the loose paint on the wall that you can.
Apply CONCRETE BONDER to the bare cinder blocks and around the holes you are about to patch. Concrete bonder is a primer to give improved adhesion between masonry surfaces. Dampen the surface and apply the bonder with a roller or brush and wait until it becomes tacky (not dry) before applying the patching cement. Work in small areas so the bonder does not become too dry before coating with patching material.
Use wire mesh, like 1/2″ hardware cloth or chicken wire, and stuff it in the holes in the cinder blocks. Apply the patching cement into and around the wire mesh working from the center to the edges. Make sure the edges of the holes are packed with the patching cement to increase the bond to the old block.
Do not be in a hurry to paint the repaired area once the repair is complete. Lime will leach out of the cement for several weeks making paint adhesion a problem.