Most of the time, this can be superficial and you may want to fix and blend in the stucco. I know this, because it happened to the home my family sold. It was just superficial and we did it to make sure the buyers wouldn't get scared by this.
Here's the company that did this for me: www.BucksCountyMasonry.com
Let them know I referred you!!
Ann Mc Guire
B. Sci. Marketing