The FactoryTalk (FT) RNADiagReceiver service in Rockwell Automation Allen-Bradley FactoryTalk CPR9 through SR5 and RSLogix 5000 17 through 20 does not properly handle the return value from an unspecified function, which allows remote attackers to cause a denial of service (service outage) via a crafted packet.
http://www.us-cert.gov/control_systems/pdf/ICSA-12-088-01.pdf
http://rockwellautomation.custhelp.com/app/answers/detail/a_id/469937