Microbiologist here.
In theory, this soup should not be eaten. You essentially made a culture liquid such as we use in the lab to feed bacterial colonies
However.
1. How cold is your kitchen? Temperature counts for a lot in bacterial multiplication.
2. Did you lift the lid at all after it boiled? Was the lid in place the entire night? If the boiled soup was never in contact with outside air, which goes a long way towards sterilization, it has less risk of contamination from spores or bacteria in the air.
My kitchen is the coldest part of my house and I know not to lift the lid of a boiled soup pot I make for the next day. So I would re-boil for at least 10 minutes, and consume.
But I do NOT officially condone this for you, since I don't know how warm your kitchen is, and whether people trifled with your soup.
PS: certain bacterial spores and certain toxins resist boiling temps, but that's a rare occurrence. Anthrax is hard to get rid of.