The Panthers (8-16, 5-6) snapped a two-game losing streak and beat the Vikings for the 10th straight game.
Hanson hit a 3-pointer 15 seconds into the overtime period for a 50-47 Milwaukee advantage, and the Panthers pulled ahead before Bullock scored with 1:04 left to make it 57-56.
Cleveland State's Raheem Moss missed an attempt at a game-winning shot at the buzzer.
Smith hit two free throws with 2:32 remaining in regulation to put the Panthers ahead 47-45, but Victor Morris, fouled by Hanson on a drive, tied it at 47-47 by making two free throws with 30 seconds left to force the overtime.
The Panthers led 23-18 at the half after the missed 15 of their first 17 shots.
Cleveland State outscored Milwaukee 8-3 to open the second half and tie the game at 26-26 on a basket by Patrick Tatham, but Paige Paulsen, Massiah and Hanson scored consecutive baskets to put the Panthers ahead 32-26.