The answer to 'why is my garbage disposal overflowing' is that the disposal is likely clogged or jammed, preventing water from draining properly. This can be caused by food debris, foreign objects, or a buildup of grease and grime in the disposal or drain pipe.
Some common symptoms of an overflowing garbage disposal include water backing up in the sink, a foul odor, or the disposal making strange noises when running. To fix the issue, you'll need to clear the clog and get the disposal functioning normally again.