The StartServiceCtrlDispatcher function in the cvpnd service (cvpnd.exe) in Cisco VPN client for Windows before 5.0.06.0100 does not properly handle an ERROR_FAILED_SERVICE_CONTROLLER_CONNECT error, which allows local users to cause a denial of service (service crash and VPN connection loss) via a manual start of cvpnd.exe while the cvpnd service is running.
http://www.vupen.com/english/advisories/2009/3296
http://tools.cisco.com/security/center/viewAlert.x?alertId=19445