The remote host is running a kernel which is vulnerable to a remote denial of service. The Linux kernel handles all the low-level functionality of the Operating System. This version of the kernel is vulnerable to a flaw wherein a remote attacker can forge source IP addresses in such a way as to create a very long routing hash chain. An attacker, exploiting this flaw, would need the ability to craft TCP/IP packets destined to (or through) the Linux kernel. A successful attack would shut down the server.