backdoor menu on conexant chipset dsl router (Zoom X3)
From: Adam Laurie (adam_at_algroup.co.uk)
Date: 07/06/04
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Date: Tue, 06 Jul 2004 13:37:44 +0100 To: bugtraq@securityfocus.com, full-disclosure@lists.netsys.com, Adam Laurie <adam@algroup.co.uk>
i have just installed an adsl modem sold under the brand of Zoom X3
http://www.zoom.com/products/adsl_overview.html
and was apalled to find that an nmap scan of the external address
immediately came up with the following:
PORT STATE SERVICE
23/tcp open telnet
80/tcp open http
254/tcp open unknown
255/tcp open unknown
ports 23 and 80 give access to the configuration menu and html interface
as would be expected, but, although you can control access to the html
interface, there is no control over the telnet port other than password.
worse still, telnetting to port 254 gives you access to another menu,
which identifies itself as "ATU-R ACCESS RUNNER ADSL TERMINAL (Annex A)
3.27", and uses the *DEFAULT* HTML management password, even if you have
changed it to something else. i.e. changing the HTML password does not
change this one. from this menu you can change DSL settings and issue a
complete "Factory Reset". there is a menu option to change the password,
but this does not appear to work.
port 255 accepts connections, but I have not investigated further.
at the minimum this carries a risk of a trivial DOS attack (factory
reset and everthing stops working), and may actually have other more
serious implications.
i am disgusted that in this day and age products like this are still
being shipped with such basic insecurities, and, accordingly, will not
be wasting my time by looking into it any further, and will be taking
the router back and exchanging it for something (hopefully) better
thought out.
to their credit, Zoom responded immediately with a workaround when i
reported the problem, so they are clearly already aware. fyi, the
workaround is to create dummy "Virtual Servers" on each of the ports
that blackhole any incoming connections. this appears to work.
connexant list several other high profile retail modem manufacturers and
pc oems, so i leave it as an exercise for the reader to work out other
manufacturer/vulnerability combinations.
http://www.conexant.com/support/md_supportlinks.html
enjoy,
Adam
-- Adam Laurie Tel: +44 (20) 8742 0755 A.L. Digital Ltd. Fax: +44 (20) 8742 5995 The Stores http://www.thebunker.net 2 Bath Road http://www.aldigital.co.uk London W4 1LT mailto:adam@algroup.co.uk UNITED KINGDOM PGP key on keyservers
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