Is the husband sinful for his divorced wife who married during her waiting period without his knowledge, and is he obligated to pay maintenance or deferred dower?

A woman's marriage during her iddah is null and void, and they must be separated. She must complete the remainder of her iddah from the first husband, and then observe a new iddah from the second husband after completing the first iddah. The maintenance of the wife during her iddah is obligatory upon the first husband, and he is obligated to pay her deferred dowry if there is any.