The DHCP client (udhcpc) in BusyBox before 1.20.0 allows remote DHCP servers to execute arbitrary commands via shell metacharacters in the (1) HOST_NAME, (2) DOMAIN_NAME, (3) NIS_DOMAIN, and (4) TFTP_SERVER_NAME host name options.
http://downloads.avaya.com/css/P8/documents/100158840
http://rhn.redhat.com/errata/RHSA-2012-0810.html
http://seclists.org/fulldisclosure/2019/Jun/18
http://seclists.org/fulldisclosure/2020/Aug/20
http://secunia.com/advisories/45363
http://www.busybox.net/news.html
http://www.mandriva.com/security/advisories?name=MDVSA-2012:129
http://www.securityfocus.com/bid/48879
https://bugs.busybox.net/show_bug.cgi?id=3979