Exterior stucco paint can have cracks due to age, or because of moisture issues. Stucco is not an even, smooth surface, but rather is very porous. Stucco also expands and contracts, which over time will cause the exterior paint to crack. If you have one particular area that is cracked, you can simply repair it by removing the exterior portion with a sand blaster, clean, reapply the stucco plaster, allow it dry, then paint it again. When you paint over the patch it will not be visible, and the paint will give added protection.