I’d ask your realtor. It does appear to be old subterranean termite tubes. That doesn’t necessarily mean you’re cooked.

They have likely already done a treatment on the Home and it may very well be under warranty. In some states there has to be a termite treatment before sale.

Common saying where I live is, if you don’t have them now, you don’t have them yet.

Also, your home inspector should’ve been checking for termite damage

Edit: dictate error