Cisco Unified Communications Manager (aka CUCM, formerly CallManager) before 6.1(1) allows remote attackers to cause a denial of service (voice-services outage) via a malformed header in a SIP message, aka Bug ID CSCsi46466.
http://www.securitytracker.com/id?1022775
http://www.securityfocus.com/bid/36152
http://www.cisco.com/en/US/products/products_security_advisory09186a0080af2d11.shtml