It's not a lens issue but one of isolating the windshield glass that the lens is looking through so that no light can hit it. Best would be some kind of conical or tubular black shround that optically "seals" the front of the camera to the windshield. I would think a carefully fashioned cone of black construction paper would do it. Possibly just a flat piece of something flat black directly under the area of the glass that the lens is looking through. For example a roughly level ~4" square piece of black construction paper taped to the windshield below and in front of the lens, extending back to the camera and taped to it.
Or, more clumsily and temporarily, identify the area of the dash it is seeing and cover that in dark fabric. Sometimes when I've got a running videocam sitting on the dash of a car I can fix all this with a dark-colored jacket.
