Sophos XG Firewall (SF01V) Cross Site Scripting

`Document Title:  
===============  
Sophos XG Firewall (SF01V) - Persistent Web Vulnerability  
  
  
References (Source):  
====================  
http://www.vulnerability-lab.com/get_content.php?id=1734  
  
ID: 5740075  
  
  
Release Date:  
=============  
2016-04-25  
  
  
Vulnerability Laboratory ID (VL-ID):  
====================================  
1734  
  
  
Common Vulnerability Scoring System:  
====================================  
3.5  
  
  
Product & Service Introduction:  
===============================  
Sophos XG Firewall provides unprecedented visibility into your network, users, and applications right from the all-new control center.   
You also get rich on-box reporting and the option to add Sophos Firewall Manager and iView for centralized management and reporting   
across multiple Firewalls. Displays the real-time status of system performance, services, connections, and other system parameters.   
Green indicates everything is fine, orange indicates a warning, and red indicates something needs immediate attention. Each item is   
clickable to reveal additional details and graphs, as well as helpful system and network tools you can use for troubleshooting   
purposes such as ping, trace route, packet capture, command-line access, and much more.  
  
(Copy of the Vendor Homepage: https://www.sophos.com/en-us/products/unified-threat-management.aspx )  
  
  
Abstract Advisory Information:  
==============================  
An independent vulnerability laboratory researcher discovered an application-side validation vulnerability in the official Sophos XG Firewall (SF01V) appliance web-application.  
  
  
Vulnerability Disclosure Timeline:  
==================================  
2016-02-17: Researcher Notification & Coordination (Lawrence Amer)  
2016-02-18: Vendor Notification (Sophos Security Team)  
2016-04-25: Public Disclosure (Vulnerability Laboratory)  
  
  
Discovery Status:  
=================  
Published  
  
  
Affected Product(s):  
====================  
  
Exploitation Technique:  
=======================  
Remote  
  
  
Severity Level:  
===============  
Medium  
  
  
Technical Details & Description:  
================================  
A persistent cross site scripting web vulnerability has been discoverd in the official Sophos XG Firewall (SF01V) appliance web-application.  
The security issue allows remote attackers to inject own malicious script codes on the application-side of the affected service module.  
  
The vulnerability is located in the `Protection - Web Protection - Web Content Filter - General Configuration - Override Default Denied Message` module.   
Remote attackers and low privileged web-application user accounts are able to inject own malicious script code context as notification value of the   
Blocked Access Request. The data of the POST method request in the nody of message text, executes without a secure encoding or a restriction in the   
body of message in the web-application appliance. The persistent execution of the script code occurs in [Default Denied Message] that gets send by   
the appliances directly to users.  
  
The security risk of the persistent validation vulnerability is estimated as high with a cvss (common vulnerability scoring system) count of 3.5.   
Exploitation of the persistent input validation web vulnerability requires a privileged web-application user account and low or medium user interaction.   
Successful exploitation of the vulnerability results in session hijacking, persistent phishing, persistent external redirects to malicious source and   
persistent manipulation of affected or connected application modules.  
  
Request Method(s):  
[+] POST  
  
Vulnerable Module(s):  
[+] Protection - Web Protection - Web Content Filter - General Configuration - Override Default Denied Message  
  
Vulnerable Parameter(s):  
[+] message body  
  
  
Proof of Concept (PoC):  
=======================  
Persistent Web Vulnerability can be exploited by remote attackers with privileged web-application user account and low or medium user interaction.  
For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue.  
  
Manual steps to reproduce the vulnerability ...  
1. goes to : Protection > Web Protection > Web Content Filter> General Configuration  
2. Choose the Override Default Denied Message input field   
3. Message HTML Input: [POC]  
Note: '><iframe src="http://vulnerability-lab.com" onload=alert(document.cookie)<  
4. After saving all users get it as default message of blocked requests as notification message  
5. Successful reproduce of the vulnerability!   
  
  
PoC:  
<b><BR><font class=accessdeniedtextfont >This is a message from the IT Department. <BR><BR>The web site you are trying to access: '><iframe src="http://vulnerability-lab.com" onload=alert(document.cookie)< <BR></font><font class=accessdeniedcategoryfont >{url}</font><BR><font class=accessdeniedtextfont >is listed as a site within the category </font><font class=accessdeniedcategoryfont>{category}</font><BR><BR><font class=accessdeniedtextfont > Current Internet Access Configuration for you does not allow visiting sites within this category at this time.<BR><BR>If the website has been erroneously blocked, please <a href="#" class="accessdeniedcategoryfont" onclick="callReevaluationFunction()">submit</a> it for re-evaluation.</font></b>  
  
  
  
Solution - Fix & Patch:  
=======================  
The vulnerability can be patched by a secure parse and encode of the vulnerable input field context.  
Encode all inputs and restrict the input by disallowing the usage of special chars.  
Parse also the outgoing values for the user notification by the appliance service itself to prevent malicious attack scenarios.  
  
  
Security Risk:  
==============  
The security risk of the application-side input validation web vulnerability in the sophos xg firewall appliance web-application is estimated as medium. (CVSS 3.5)  
  
  
Credits & Authors:  
==================  
Lawrence Amer - ( http://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 for   
consequential or incidental damages so the foregoing limitation may not apply. We do not approve or encourage anybody to break any vendor licenses,   
policies, deface websites, hack into databases or trade with fraud/stolen material.  
  
Domains: www.vulnerability-lab.com - www.vuln-lab.com - www.evolution-sec.com  
Contact: [email protected] - [email protected] - [email protected]  
Section: magazine.vulnerability-db.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/  
  
Any modified copy or reproduction, including partially usages, of this file 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 (feed), modify, use or edit our material contact   
([email protected] or [email protected]) to get a permission.  
  
Copyright © 2016 | Vulnerability Laboratory - [Evolution Security GmbH]™  
  
  
  
--   
VULNERABILITY LABORATORY - RESEARCH TEAM  
SERVICE: www.vulnerability-lab.com  
CONTACT: [email protected]  
  
`