The fetch_url function in usr.bin/ftp/fetch.c in tnftp, as used in NetBSD 5.1 through 5.1.4, 5.2 through 5.2.2, 6.0 through 6.0.6, and 6.1 through 6.1.5 allows remote attackers to execute arbitrary commands via a | (pipe) character at the end of an HTTP redirect.
https://www.exploit-db.com/exploits/43112/
https://security.gentoo.org/glsa/201611-05
http://support.apple.com/HT204244
http://secunia.com/advisories/62260
http://secunia.com/advisories/62028
http://seclists.org/oss-sec/2014/q4/464
http://seclists.org/oss-sec/2014/q4/459
http://lists.opensuse.org/opensuse-updates/2014-11/msg00029.html
http://lists.apple.com/archives/security-announce/2015/Jan/msg00003.html
http://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2014-013.txt.asc