Suppose that in FreeBSD (or linux maybe) there is a non-privileged normal user (non-superuser). And there is a telnet standalone (I know that telnet is usually run under inetd) running under (owned by) this user. (Suppose that there was no original, root-owned telnet running.) This telnet server is programmed so that it does not check ld_* environment variables before passing it to /bin/login owned by root that has setuid set up.
The question would be: 1. Will this telnet work? 2. If it does work, will it even be able to pass environment variables to /bin/login?