ISC DHCP client program dhclient allows remote attackers to execute arbitrary commands via shell metacharacters.
https://exchange.xforce.ibmcloud.com/vulnerabilities/4772
http://www.securityfocus.com/bid/1388
http://www.novell.com/linux/security/advisories/suse_security_announce_56.html
http://www.debian.org/security/2000/20000628
http://archives.neohapsis.com/archives/bugtraq/2000-07/0014.html
http://archives.neohapsis.com/archives/bugtraq/2000-06/0247.html