Public Vulnerability Reports

3Com OfficeConnect Remote 812 ADSL Router Telnet Protocol DoS Vulnerability



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.


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

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.


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

More information about the 3Com OfficeConnect Remote 812 ADSL Router is
available at


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



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.


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 (, which standardizes names for
security problems.


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


Rafel Ivgi is credited with this discovery.

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Copyright © 2004 Verisign, Inc.

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