In the nfs-utils package, providing support files for Network File System (NFS) including the rpc.statd daemon, the directory /var/lib/nfs is owned by statd:nogroup. This directory contains files owned and managed by root. If statd is compromised, it can therefore trick processes running with root privileges into creating/overwriting files anywhere on the system.
For Debian 7 Wheezy, these problems have been fixed in version 1.2.6-4+deb7u1.
We recommend that you upgrade your nfs-utils packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/