Cisco Unified Communications Manager (aka CUCM, formerly CallManager) 4.x, 5.x before 5.1(3g), 6.x before 6.1(4), 7.0 before 7.0(2), and 7.1 before 7.1(2); and Cisco Unified Presence 1.x, 6.x before 6.0(6), and 7.x before 7.0(4); allows remote attackers to cause a denial of service (TCP services outage) via a large number of TCP connections, related to "tracking of network connections," aka Bug IDs CSCsq22534 and CSCsw52371.
http://www.vupen.com/english/advisories/2009/2915
http://www.securitytracker.com/id?1022775
http://www.securityfocus.com/bid/36676
http://www.securityfocus.com/bid/36152
http://www.cisco.com/en/US/products/products_security_advisory09186a0080afc930.shtml
http://www.cisco.com/en/US/products/products_security_advisory09186a0080af2d11.shtml
http://securitytracker.com/id?1023018
http://secunia.com/advisories/37039