Tenda, Dlink & Tplink TD-W8961ND - DHCP XSS Vulnerability

Document Title:
===============
Tenda, Dlink & Tplink TD-W8961ND - DHCP XSS Vulnerability


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=1990

http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2018-20372
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2018-20373

CVE-ID:
=======
CVE-2018-20372


Release Date:
=============
2016-11-28


Vulnerability Laboratory ID (VL-ID):
====================================
1990


Common Vulnerability Scoring System:
====================================
3.5


Abstract Advisory Information:
==============================
The vulnerability laboratory research team discovered a persistent xss vulnerability in the Tenda, Dlink & Tplink 1.0.1 TD-W8961ND & ADSL2+ Modem Routers web-application.


Vulnerability Disclosure Timeline:
==================================
2016-11-28:	Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Low


Technical Details & Description:
================================
Persistent cross site scripting vulnerability has been discovered in Tenda 1.0.1 ADSL Modem Routers.
The vulnerability allows remote attackers and local privileged account to inject malicious script codes 
on the application-side to manipulate the router dhcp hostnames. 

Attackers are able to inject malicious code into the current list of DHCP clients on view, by modifying 
the DHCP hostname into valid xss payload. The execution of vulnerability occurs on the application-side 
on view events. Due to our investigation, we discovered that all models with the firmware v1.x on the 
web gui are affected by the security vulnerability. Remote attackers can for example make special crafted 
malicious pages with POST method requests to manipulate the dhcp hostname listing and client view.

The security risk of the issue is estimated as medium with a cvss (common vulnerability scoring system) count of 3.5. 
Exploitation of the vulnerability requires no privilege web-application user account and only low user interaction. 
Successful exploitation of the vulnerability results in phishing attacks, session hijacking, persistent external redirect 
to malicious sources and persistent manipulation of affected or connected web module context.

Request Method(s):
[+] POST

Vulnerable Module(s):
[+] DHCP Client List 
[+] DHCP settings

Vulnerable Parameter(s):
[+] Hostnames


Proof of Concept (PoC):
=======================
Persistent vulnerability can be exploited by remote attackers with low privileged application user account and low user interaction.
For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue.


Manaul steps to reproduce the vulnerability ... (local)
1. Open the Router UI
2. Login as basic account
3. Open the DHCP List module via settings
4. Inject a payload to the hostnames input field
5. Save the input
6. Now the list becomes visible with all clients and the payload executes within the context
7. Successful reproduce of the vulnerability!

The following code is a bash script working on supported Linux OS to change the name of DHCP hostnames to a xss payload. 
Save the file into vulnerablity.sh, then chmod +x vulnerability.sh.

PoC: Exploit
#!/bin/bash
GREEN=$(tput setaf 2 && tput bold)
BLUE=$(tput setaf 6 && tput bold) 
echo $BLUE"[+] Persistent XSS DHCP Exploiter via Routers"
echo $GREEN"[+] Vulnerability founded by : Lawrence Amer " 
echo -n $BLUE"[~] type XSS Payload here :"
read -e xss 
echo $xss > /etc/hostname
echo $GREEN"[+]DHCP HOST NAME IS WRITTEN"


Video: https://www.youtube.com/watch?v=HUM5myJWbvc


Solution - Fix & Patch:
=======================
The xss vulnerability can be patched by a secure parse of the hostnames client parameters.
Restrict the input and disallow the usage of special chars to prevent the injection point.
Parse as well the hostnames output location in the active dhcp clients list.


Security Risk:
==============
The security risk of the persistent xss web vulnerability in the router web-application is estimate as medium. (CVSS 3.5)


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Lawrence Amer (https://www.vulnerability-lab.com/show.php?user=Lawrence%20Amer)


Disclaimer & Information:
=========================
The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all warranties, either expressed 
or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability-Lab or its suppliers are not liable 
in any case of damage, including direct, indirect, incidental, consequential loss of business profits or special damages, even if Vulnerability-Lab 
or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability mainly for 
consequential or incidental damages so the foregoing limitation may not apply. We do not approve or encourage anybody to break any licenses, policies, 
deface websites, hack into databases or trade with stolen data.

Domains:    www.vulnerability-lab.com 		- www.vuln-lab.com 						- www.evolution-sec.com
Section:    magazine.vulnerability-lab.com 	- vulnerability-lab.com/contact.php 				- evolution-sec.com/contact
Social:	    twitter.com/vuln_lab		- facebook.com/VulnerabilityLab 				- youtube.com/user/vulnerability0lab
Feeds:	    vulnerability-lab.com/rss/rss.php 	- vulnerability-lab.com/rss/rss_upcoming.php 			- vulnerability-lab.com/rss/rss_news.php
Programs:   vulnerability-lab.com/submit.php 	- vulnerability-lab.com/list-of-bug-bounty-programs.php 	- vulnerability-lab.com/register.php

Any modified copy or reproduction, including partially usages, of this file, resources or information requires authorization from Vulnerability Laboratory. 
Permission to electronically redistribute this alert in its unmodified form is granted. All other rights, including the use of other media, are reserved by 
Vulnerability-Lab Research Team or its suppliers. All pictures, texts, advisories, source code, videos and other information on this website is trademark 
of vulnerability-lab team & the specific authors or managers. To record, list, modify, use or edit our material contact (admin@) to get a ask permission.

				    Copyright © 2016 | Vulnerability Laboratory - [Evolution Security GmbH]™