Public Vulnerability Reports

3Com OfficeConnect Remote 812 ADSL Router Telnet Protocol DoS Vulnerability

05.26.04

BACKGROUND

The 3Com OfficeConnect Remote 812 ADSL Router is a standalone
bridge/router, with interfaces to a Local Area Network and an ADSL
interface to a Wide Area Network.

DESCRIPTION

Remote exploitation of a buffer overflow in firmware release 1.1.9.4 of
3Com's OfficeConnect Remote 812 ADSL Router could allow a denial of
service.

By sending a specially formed long string to the telnet port of a
vulnerable device containing Telnet escape sequences, it is possible to
get it to either reboot or stop handling packets. If the device does not
reboot spontaneously, it will require a manual reboot before continuing
normal operation.

ANALYSIS

Successful exploitation allows an attacker to stop the device from
responding thereby preventing legitimate users from accessing the
internet.

More information about the 3Com OfficeConnect Remote 812 ADSL Router is
available at
http://www.3com.com/products/en_US/detail.jsp?tab=support&pathtype=support&sku=3CP4144.

DETECTION

3Com OfficeConnect Remote 812 ADSL Router with the last firmware patch
available has been confirmed vulnerable.

WORKAROUND

S

A previously given workaround for other issues with the http interface
is available at the link shown. This shows how to configure the router
to prevent external access to the http port. By changing occurences of
port 80 into port 23, this method should also work for the telnet port.

http://support.3com.com/infodeli/tools/remote/ocradsl/http_filtering.pdf

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-0476 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

02/18/2004   Exploit acquired by iDEFENSE
03/08/2004   iDEFENSE Clients notified
03/11/2004   Initial vendor notification - no response
03/30/2004   Secondary vendor notification - no response
05/26/2004   Public Disclosure

CREDIT

Rafel Ivgi is credited with this discovery.

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LEGAL NOTICES

Copyright © 2004 Verisign, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDEFENSE. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
email customerservice@idefense.com for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.