They are nasty. I had a hive of them in an open area of an addition onto the house. Sprayed the heck out of them. Killed a ton that way, but there were more left. When the colder weather arrived, I plugged the area with that foam spray. Problem solved.
Yes, they’re very aggressive. Even worse in my experience, is the bald-faced hornet, which is actually a type of yellow jacket (wasp). I was on antibiotics for weeks after being bitten by one that followed me into the house.