Cisco Unified Communications Manager (aka CUCM, formerly CallManager) 6.x before 6.1(5), 7.x before 7.1(3a)su1, and 8.x before 8.0(1) allows remote attackers to cause a denial of service (process failure) via a malformed SCCP (1) RegAvailableLines or (2) FwdStatReq message with an invalid Line number, aka Bug ID CSCtc47823.