Remove the cupboard door from the frame by unscrewing the hinges. Leave the hinges attached to the door.
Pour about 1 teaspoon of wood glue into a saucer. Dip one end of a toothpick in wood glue to coat about 1 inch of the toothpick. Insert the glued end of the toothpick into the screw hole on the cabinet frame. Continue gluing and inserting toothpicks until no more toothpicks will fit in the screw hole. Tap the toothpicks with a mallet to drive them as far as you can into the hole. Repeat to fill remaining holes with glued toothpicks.
Allow the glue to dry, according to the manufacturer's directions. Grasp the toothpicks and snap them off by acutely bending them. Use a serrated knife as a saw to cut any remaining pieces of toothpicks so they are flush with the cabinet frame.
Reposition the cupboard door on the frame. Align the screw holes in the hinges to the fortified holes in the frame. Pass the tip of a screw through an installation hole in the hinge, then into the frame. Tighten by turning the screw clockwise. Repeat to finish screwing the hinge and remaining hinges to the cupboard frame.