The SIP channel driver (chansip) in Asterisk Open Source 1.4.x before 1.4.11, AsteriskNOW before beta7, Asterisk Appliance Developer Kit 0.x before 0.8.0, and s800i (Asterisk Appliance) 1.x before 1.0.3 allows remote attackers to cause a denial of service (memory exhaustion) via a SIP dialog that causes a large number of history entries to be created.