Trivial Telnet authentication bypass exposes devices to complete takeover

telnetd server invokes /usr/bin/login (normally running as root) passing the value of the USER environment variable received from the client as the last parameter,” Simon Josefsson, a GNU contributor who submitted the patch, said on the OSS-SEC mailing list. “If the client supplies a carefully crafted USER environment value being the string “-f root“, and passes the telnet(1) -a or