FreeBSD Security Advisory (FreeBSD-SA-10:06.nfsclient.asc)

The remote host is missing an update to the system as announced in the referenced advisory FreeBSD-SA-10:06.nfsclient.asc
Upgrade your system to the appropriate stable release or security branch dated after the correction date
The Network File System (NFS) allows a host to export some or all of its file systems so that other hosts can access them over the network and mount them as if they were on local disks. FreeBSD includes server and client implementations of NFS. The NFS client subsystem fails to correctly validate the length of a parameter provided by the user when a filesystem is mounted.