Multiple format string vulnerabilities in eStara SIP softphone allow remote attackers to cause a denial of service (hang) via SIP INVITE requests with format string specifiers in the SDP session description, as demonstrated using (1) the field name, (2) the o field (owner/creator and session identifier), or (3) the m field (media name and transport address).
https://exchange.xforce.ibmcloud.com/vulnerabilities/24678
http://www.vupen.com/english/advisories/2006/0607
http://www.securityfocus.com/bid/16629
http://www.securityfocus.com/archive/1/424943/100/0/threaded