If the source is not a connection from above then your disposal needs to be replaced. Try cupping your hands around the very top under the sink while running water. The ring that seals the gasket turns clockwise to tighten. The only other repairable leak would be where the piping comes out the side. There can also be a smaller dishwasher drain hose above that.
If there is no item stuck in the blades of the disposal obtain the Allen wrench that should be attached to your disposal or that came with it. There is a breaker socket located on the bottom of most disposal brands. Place the Allen wrench in the breaker socket and turn it back and forth. By doing this you may be able to unlock the source of the problem. Just be certain that the disposal is not turned on when doing this.
Another common cause for a leaking garbage disposal is the disposal flange. A leak at the very most upper area of the garbage disposal could be the garbage disposal flange which goes through the sink. A garbage disposal flange should be sealed with Plumber’s putty and then tightened from underneath the sink. If this is not tight enough or if it has managed to come loose (which can happen) then the garbage disposal will have to be taken down so the flange can be resealed and then the garbage disposal can be rehung.