Is the rot accompanied by a black patch at the blossom end of the fruit? If so, it might be Blossom End Rot, which is caused by calcium deficiency, the same as in tomatoes.
There are other diseases that can cause the fruit to rot on the vine, but they usually show in the leaves first. Are the leaves big and green and healthy?
It’s also possible that the plant decided that these fruits weren’t pollinated well enough for its liking, so it self-aborted them. But my gut instinct is that this is unlikely in your case. Most likely, your squash just need more calcium.
Not blossom end rot.
I should have specified....it is literally the tip end of the swuash shrivellin up....wrinkly....gets soft and wrinkly.
I ate the big one after cutting the arinkly tip off.
Not rotten at all..just shriveling.