There is no easy solution to this problem. Any heat rising from the basement will warm the floors above. With a cantilever floor, there is no heat coming from below, but just cold air. There are some things that can be done to improve the situation. The first thing to do is remove the quarter-round molding where the inside wall and floor meet. Fill that space with caulking. Outdoors, underneath the cantilevered section, caulk all cracks, and add sheets of rigid foam paneling and another layer of plywood over that. If you have forced-air heating, extend the duct to run through the floor area that is affected. If that is too difficult to get to, electric heating coils or electric heating blankets made to install under rugs could do the same job. One last trick that will improve the situation is an old one-lay a rug on the floor.