The remote VoIP server is vulnerable to a denial of service attack.
According to the version in its SIP banner, the version of Asterisk running on the remote host is potentially affected by a vulnerability that could allow a remote attacker to crash the server. This issue may be exploited when the attacker has a valid SCCP (Skinny) ID and closes a connection when in certain call states. A null pointer is left behind and can cause the server to crash when the pointer is later dereferenced.
Upgrade to Asterisk 10.5.1 or apply the patches listed in the Asterisk advisory