The nosuid mount option specifies that the filesystem cannot contain setuid files. Since the /var/tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /var/tmp.
Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/tmp partition. See the fstab(5) manual page for more information. Run the following command to remount /var/tmp: # mount -o remount,nosuid /var/tmp