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.