Sophos XG Firewall (SF01V) - Persistent Web Vulnerability

[Vulnerability Lab <research@xxxxxxxxxxxxxxxxxxxxx>]

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 )


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=========================
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