Barracuda Networks Cloud Series Script Insertion

`Document Title:  
===============  
Barracuda Networks Cloud Series - Filter Bypass Vulnerability  
  
  
References (Source):  
====================  
http://www.vulnerability-lab.com/get_content.php?id=754  
  
Barracuda Networks Security ID (BNSEC): 731  
  
  
Release Date:  
=============  
2015-01-19  
  
  
Vulnerability Laboratory ID (VL-ID):  
====================================  
754  
  
  
Common Vulnerability Scoring System:  
====================================  
4.1  
  
  
Abstract Advisory Information:  
==============================  
The Vulnerability Laboratory Research Team discovered a filter bypass vulnerability in the official Barracuda Cloud Series Products.  
  
  
Vulnerability Disclosure Timeline:  
==================================  
2015-01-19: Public Disclosure (Vulnerability Laboratory)  
  
  
Discovery Status:  
=================  
Published  
  
  
Affected Product(s):  
====================  
Barracuda Networks  
Product: Cloud Control Center 2014 Q2  
  
  
Exploitation Technique:  
=======================  
Remote  
  
  
Severity Level:  
===============  
Medium  
  
  
Technical Details & Description:  
================================  
A filter bypass vulnerability has been discovered in the official Barracuda Networks Cloud Series Appliance Applications 2014-Q1.  
The filter bypass issue allows an attacker to bypass the secure filter validation of the service to execute malicious script codes.   
  
The barracuda filter blocks for example standard iframes, scripts and other invalid code context: The cloud service has a own exception-handling   
to parse or encode malicious injected web context. The mechanism filters the first request and sanitizes the output in every input field.  
  
During a pentest we injected a standard iframe to check and provoke the validation. The frame got blocked! In the next step the attacker splits (%20%20%20)   
the request and injects at the end an onload frame to an external malicious source. The second iframe with the onload alert executes the script codes after   
the validation encoded only the first script code tag. The second script code tag can bypass the applicance filter mechanism and executes in the web context   
of affected modules. The secure validation does not recognize a splitted request which results in client-side and application-side script code execution in   
the cloud series products.  
  
The security risk of the filter bypass vulnerability is estimated as medium and the cvss (common vulnerability scoring system) count is 4.1 (medium).   
Exploitation of the filter bypass vulnerability requires a low privileged application user account with restricted access and low user interaction.   
Successful exploitation of the vulnerability results in session hijacking, persistent phishing, persistent external redirects and persistent manipulation   
of affected or connected module context.  
  
Vulnerable Request Method(s):  
[+] POST & GET  
  
  
Proof of Concept (PoC):  
=======================  
The filter bypass web vulnerability can be exploited by local privileged user accounts and remote attackers with low or medium user interaction.   
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.  
  
PoC:   
<iframe src=a>%20%20%20%20\"><iframe src=http://vuln-lab.com onload=alert("VL") <  
  
PoC:   
<script language=JavaScript>m='%3Ciframe%20src%3Da%3E%2520%2520%2520%2520%5C%22%3E%3Ciframe%20src%3Dhttp%3A//vuln-lab.com%20onload%3Dalert%28%22VL%22%29%20%3C';d=unescape(m);document.write(d);</script>  
  
  
Solution - Fix & Patch:  
=======================  
The issue can be patched by a secure validation of the full message input body context of any input or request method attempt.  
Ensure that the validaton does not only encode the first injected script code since a empty char arrives. Filter all web context   
that runs through the requesting procedure and parse separatly to prevent script code injection attacks.  
  
Note: Barracuda Networks patched the vulnerability and acknowledged the researcher. Updates are available in Barracuda Labs and the Customer Service.  
  
  
Security Risk:  
==============  
The security risk of the filter bypass web vulnerability in the barracuda cloud product series is estimated as medium. (CVSS 4.1)  
  
  
Credits & Authors:  
==================  
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected]) [www.vulnerability-lab.com]  
  
  
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=========================  
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