The /var/tmp directory is a world-writable directory. Bind-mount
it to /tmp in order to consolidate temporary storage into one
location protected by the same techniques as /tmp. To do so, edit
/etc/fstab and add the following line:
/tmp /var/tmp none rw,nodev,noexec,nosuid,bind 0 0
See the mount(8) man page for further explanation of bind mounting.