A flaw was discovered in coturn, a TURN and STUN server for VoIP. By default coturn does not allow peers on the loopback addresses . A remote attacker can bypass the protection via a specially crafted request using a peer address of "0.0.0.0" and trick coturn in relaying to the loopback interface. If listening on IPv6 the loopback interface can also be reached by using either [::1] or [::] as the address.