That is a foam surround which can be repaired. If the surrounds are not otheriwse deteriorating the hole can just be repaired, if the surrounds are crumbling the entire surround can be replaced.

Carefully remove the driver and wires. While holding some wax paper to the backside of the hole sparingly apply silicone sealant to the hole. Then hold another piece of wax paper over the silicone and lightly pinch to force the sealant evenly into the damaged area and to smooth the surface. Leave the wax paper in place while it dries for around 24 hours. Carefully peel the wax paper off and repeat if there are gaps or the hole did not seal completely. Reattach the wires and reinstall the driver into the cabinet.