New York Consolidated Laws, Real Property Actions and Proceedings Law - RPA § 1313. Permissible defendants

Any person who is liable to the plaintiff for payment of the debt secured by the mortgage may be made a defendant in the action.  The state may be made a party defendant to an action for the foreclosure of a mortgage on real property, where it has an interest in or a lien on the property subsequent to the lien of the mortgage sought to be foreclosed in said action, in the same manner as a private person.