This is extremely common, and one of the reasons that using SSN for credit reports is a horrible practice. The only way for someone to dispute the debts is to report their parents to the authorities, which is a horrible position to be in when you’re freshly 18. The real solution would be a simple age check, to verify if the person applying for the loan is actually 18. But that ~~is apparently too difficult~~ would prevent banks from saddling literal children with mountains of debt.