Under Sunni law, a Muslim can marry any number of wives not exceeding four. If a Sunni Muslim marries a…

Under Sunni law, a marriage with a fifth wife while four marriages subsist is irregular (fasid), not void. The bar is temporary, and the marriage can become regular if one of the earlier marriages ends by death or divorce.

It is not valid as it stands, and the concept of voidability does not apply here. Under Shia law, by contrast, such a marriage is void.