The SJPhone SIP soft phone 1.60.303c, when installed on the Dell Axim X3 running Windows Mobile 2003, allows remote attackers to cause a denial of service (device hang and traffic amplification) via a direct crafted INVITE transaction, which causes the phone to transmit many RTP packets.
https://exchange.xforce.ibmcloud.com/vulnerabilities/35078
http://www.sipera.com/index.php?action=resources%2Cthreat_advisory&tid=217&