Denial of service in 3COM 812 DSL routers

["David F. Madrid" <idoru () videosoft net uy>]

Product affected : 3COM 812 OfficeConnect DSL routers

Firware affected :

1.1.9

2.0 ?

Description :

OfficeConnect is a router widely used in the world . Just in Spain ,
Telefonica buy more than 100000 812 routers to 3COM until 2001 to
deploy them in his ADSL lines .

The router can be rebooted due to a flaw in its web administration
interface . As no athentication is needed , every LAN user can cause
a crash and reboot of the router , stoping internet connection for
one or two minutes . A remote user can exploit it if the web interface
is available in the WAN interface of the router or if he can persuade
a user to click on a link in a forum or to visit a webpage ( as
you can always access the web interface if the connection is local
initiated , as is from the web browser ) .

I haven't tested this in another 812 router , but on mine the
buffer that holds the complete HTTP request is of 512 bytes
and is not checked if the lengh of the request is bigger that
this limit . So to reboot the router you just have to connect
to the web interface and send 512 bytes or more

perl -e 'print "A"x512;print "\n\n\n\n\n\n\n\n"' | netcat -v -n 127.0.0.1 80


You can read this advisory in Spanish in

http://nautopia.coolfreepages.com/vulnerabilidades/3com812_Web_DOS.htm


Regards ,

David F. Madrid ,
Madrid , Spain



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