Vulnerability

    Bad Cisco configuration

Affected

    Cisco 2509/2511

Description

    Albert Siersema pointed  out an old  one, but people  do configure
    Cisco this way and forget to do a:

        transport input none

    on their  'line 1  16' (or  whatever) config.   If you  are  using
    clear text  authentication with  tacacs, only  the next  lines are
    needed in the config for lines 1 20 (by Gustavo Lozano):

        line 1 20
         login tacacs

    If you use the default values ('telnet' possibly) and you have  no
    filters (stupid idea  too) on your  Cisco then someone  is able to
    use ports 2001 and  up to connect to  one of the devices  attached
    to  it.  If  this  is  a  modem  that  same person can type any AT
    command he/she wants.

Solution

    Erdinc Kaya  proposed following:  first enter  conf terminal  mode
    and then in line 1 16 enter "modem ri-is-cd" command.. it makes  a
    protection to the port 2001-2-3-4 (modem attached ports) and  when
    you  telnet  to  these  ports   the  connection  will  be   closed
    (refusing)..