Barracuda Bug Bounty #36 Firewall - Client Side Exception Handling Web Vulnerability

Type securityvulns
Reporter Securityvulns
Modified 2014-02-28T00:00:00


Document Title:

Barracuda Bug Bounty #36 Firewall - Client Side Exception Handling Web Vulnerability

References (Source):

Barracuda Networks Security ID (BNSEC): BNSEC-2398

View Video:

Release Date:


Vulnerability Laboratory ID (VL-ID):


Common Vulnerability Scoring System:


Product & Service Introduction:

The Barracuda Firewall goes beyond traditional network firewalls and UTMs by providing powerful network security, granular layer 7 application controls, user awareness and secure VPN connectivity combined with cloud-based malware protection, content filtering and reporting. It alleviates the performance bottlenecks in Unified Threat Management (UTM) appliances through intelligent integration of on-premise and cloud-based technologies. While the powerful on- premises appliance is optimized for tasks like packet forwarding and routing, Intrusion Prevention (IPS), DNS/DHCP services and site-to-site connectivity; CPU intensive tasks like virus scanning, content filtering and usage reporting benefit from the scalable performance and elasticity of the cloud.

(Copy o the Vendor Homepage: )

Abstract Advisory Information:

The Vulnerability Laboratory Team discovered a filter bypass and a persistent vulnerability in Barracuda Networks Firewall Appliance v6.1.0.016 Application.

Vulnerability Disclosure Timeline:

2013-09-26: Researcher Notification & Coordination (Benjamin Kunz Mejri) 2013-09-28: Vendor Notification (Barracuda Networks Security Team - Bug Bounty Program) 2013-10-06: Vendor Response/Feedback (Barracuda Networks Security Team - Bug Bounty Program) 2014-02-17: Vendor Fix/Patch (Barracuda Networks Developer Team) [Coordination: Dave Farrow] 2014-02-20: Public Disclosure (Vulnerability Laboratory)

Discovery Status:


Affected Product(s):

Barracuda Networks Product: Firewall Appliance Web-Application - x100 x200 x300 x400 x500 x600 & Vx

Exploitation Technique:


Severity Level:


Technical Details & Description:

A input validation web vulnerability is detected in the official Barracuda Networks Firewall Appliance Web-Application. The vulnerability allows an attacker (remote) to implement/inject own malicious persistent script codes (application side).

The vulnerability is located in the `VPN > Certificates` module when processing to request via POST to GET method manipulated `cert_error` parameters in the secure application exception-handling. The code will be directly executed in the main header on top inside of the error message. The issue impact a persistent and a non-persistent issue.

The attacker goes to the certificates area and uploads even in the restricted mode 2 pem certs, he tampers the request and exchange the upload path and drops also a invalid value to the name. The application will respond with a GET and drop a unknown error message in the exception-handling of the module. The attacker is changing the referer and includes his own code in the client-side affected parameter. Now the links in the main website will change to the error link persistent. The attacker is now able to easily click the link or request the url to execute the code inside of the exception-handling contents`>Error message.

Exploitation of the persistent web vulnerability requires low user interaction and a local low privileged web-application account. Successful exploitation of the vulnerability can lead to persistent session hijacking (customers), account steal via persistent web attacks, persistent phishing or persistent manipulation of module context.

Vulnerable Module(s): [+] VPN > Certificates

Vulnerable Parameter(s): [+] cert_error (contents:error)

Affected Module(s): [+] Exception-Handling - Error Message

Proof of Concept (PoC):

The input validation vulnerability in the exception-handling can be exploited by remote attackers with low privileged web-application user account and low user interaction. For security demonstration or to reproduce the vulnerability follow the provided steps and information below to continue.

  1. You need to request the regular module ... https://firewall.localhost:8080/cgi-bin/index.cgi?&et=1380384291&locale=en_US&encrypt_password=&user=guest&primary_tab=VPN&secondary_tab=certificates&

  2. Provoke an error inside of the regular protected exception-handling via upload pem: https://firewall.localhost:8080/cgi-bin/index.cgi?&et=1380384291&locale=en_US&encrypt_password=&user=guest&primary_tab=VPN&secondary_tab=certificates&cert_error=Unknown%20operation#key0

  3. After the redirect with the url to the error happened the attacker is able to change the exception input variable to execute own codes https://firewall.localhost:8080/cgi-bin/index.cgi?&et=1380384291&locale=en_US&encrypt_password=&user=guest&primary_tab=VPN&secondary_tab=certificates&cert_error=%3E%22%3Ciframe%20src=b%3E

PoC: Exception Handling - Error Message

<tr><td><table id="status_screen" class="status_screen"><tbody><tr><td><center><table class="status_module" cellpadding="0" cellspacing="0"><tbody><tr><td><div id="error"><b class="outlinetop"><b class="outline1"></b> <b class="outline2"></b><b class="outline3"></b><b class="outline4"></b></b><div id="contents">Error: >"<[MALICIOUS INJECTED SCRIPT CODE!])"><<br> </div><b class="outlinebottom"><b class="outline4"></b><b class="outline3"></b><b class="outline2"></b> <b class="outline1"></b></b></div></td></tr></table></center></td></tr></table></td></tr><tr style="background-color:#D9F5FF;"> <td class="config_screen" valign="top" height="400" width="100%" ><table summary="Body" border="0" width="100%" ><tr ><td> <table width=100% height=100% style="padding:2px" ><tr><td height=100%> <table cellspacing=0 cellpadding=0 class=outlined> <tr> <td class='tl'></td> <td class='tm'></td> <td class='tr'></td> </tr>

Reference(s): ../Barracuda Firewall Certificates - provoke unknown exception.htm ../Barracuda Firewall Certificates.htm ../dom1.txt ../poc.txt ../poc-session-log.txt

Picture(s): ../1.png ../2.png ../3.png

Solution - Fix & Patch:

The remote web vulnerability can be patched by a secure parse of the error message context inside of the firewall certificate error exception-handling.

Security Risk:

The security risk of the validation web vulnerability is estimated as medium to high because of the location in the secure application exception-handling.

Credits & Authors:

Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ( []

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.

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