The Nortel UNIStim IP Softphone 2050, IP Phone 1140E, and additional Nortel products from the IP Phone, Business Communications Manager (BCM), Mobile Voice Client, and other product lines, allow remote attackers to block calls and force re-registration via a resume message to the Signaling Server that has a spoofed source IP address for the phone. NOTE: the attack is more disruptive if a new spoofed resume message is sent after each re-registration.
osvdb.org/41772
secunia.com/advisories/27234
securityreason.com/securityalert/3274
support.nortel.com/go/main.jsp?cscat=BLTNDETAIL&id=654641
www.securityfocus.com/archive/1/482481/100/0/threaded
www.securityfocus.com/bid/26124
exchange.xforce.ibmcloud.com/vulnerabilities/37254
www.csnc.ch/static/advisory/csnc/nortel_IP_phone_forced_re-authentication_v1.0.txt