Multiple versions of Cisco ONS 15327 ONS 15454 and ONS 15454 SDH including 4.6(0) and 4.6(1) 4.5(x) 4.1(0) to 4.1(3) 4.0(0) to 4.0(2) and earlier versions allows remote attackers to cause a denial of service (control card reset) via a large number of TCP connections with an invalid response instead of the final ACK (TCP-ACK).