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Barracuda Application Validation Filter Bypass

Barracuda Application Validation Filter Bypass
Posted Aug 1, 2012
Authored by Benjamin Kunz Mejri, Vulnerability Laboratory | Site vulnerability-lab.com

Barracuda Appliances suffer from a validation filter bypass vulnerability.

tags | exploit, bypass
SHA-256 | c222b5b36db2aca926df6332261353a3202eb98ce3597706a147c11aa1a06dae

Barracuda Application Validation Filter Bypass

Change Mirror Download
Barracuda Appliances - Validation Filter Bypass Vulnerability




Common Vulnerability Scoring System:

The Vulnerability Laboratory Research Team discovered a input validation filter bypass vulnerability in Barracudas Network appliance products.

2012-06-09: Researcher Notification & Coordination
2012-06-10: Vendor Notification
2012-07-12: Vendor Response/Feedback
2012-07-14: Vendor Fix/Patch
2012-07-16: Public Disclosure




A filter bypass vulnerability is detected in the Barracuda Networks Appliances Applications. Remote attackers
with privileged user accounts bypass the application internal filter & exception-handling. Successful exploitation
of the vulnerability result in dbms (Server) or application (Web) compromise. Exploitation requires low or medium
user inter action & with privileged user account.

The input filter blocks persistent input attacks with a restriction/filter exception for double quotes, <>,frames,
scripts & statements. The vulnerability allows to bypass the existing input validation filter & exception handling.

The bug is located when processing to save the url path name (db stored) with attached file. The vulnerability
allows to bypass the path url name parse restriction which leads to the execution on a secound vulnerable bound
module which displays the input as output listing. The Account MyResource Display (example listing + input) & Upload
File modules are executing the earlier saved `save` path of url-path/folder which leads to the bypass of the input
validation filter & exception-handling. The result is the persistent execution of malicious script codes out of the
security appliance application context.

The vulnerability allows to bypass this method with this tricky way ...

The url path function save the context of the input path name(parsed) as client side request (GET) via URL. If the
request is getting bound with the file (POST), which is getting stored (persistent) displayed later on the overview
listings, the code will be unauthorized executed out of the security application context(persistent|server-side).

Vulnerable Module(s):
[+] MyResource, File System & File Upload Output/Input - Input Validation Filter Restriction & Listing

NOTE: The vulnerability is also located on different other security appliances on all resource listings or file uploads with url path save.

Proof of Concept:
The vulnerability can be exploited by local low privileged user accounts & with medium or high required user inter action.
For demonstration or reproduce ...

Manually ...

1. Login into for example the SSL VPN appliance
2. Switch over to the MyResources File System
3. Open via Tamper the following url ... fileSystem.do?ActionTarget=list&path=smb/random folder/
4. Now save the path and switch to new folder
5. The setting of the path has been implemented automatic. Change the Path to your scriptcode after it has been parsed.
6. Now switch after the save to the uplaod files function. Upload any random file which is bound to the malicious title.
7. Save the file and the code is getting executed in the main index of the preview in myresources.

<a href="?launchId=l7e68d5&startRow=0&
path=smb%2F%22%3E%3C[PERSISTENT SCRIPT CODE EXECUTION!]+%3C&pageSize=25&sortReverse=
amp;amp;actionTarget=list" class="columnHeader">Size</a>

... or

<span><a href="fileSystem.do?actionTarget=list&launchId=l7e68d5&path=smb/Sales%20Folder">Sales Folder
</a> / <a href="fileSystem.do?actionTarget=list&launchId=l7e68d5&path=smb/Sales%20Folder/Testing%20from%20Tri%20Opt">
Testing from Tri Opt</a> /​​​​​ <a href="fileSystem.do?actionTarget=list&
Testing%20from%20Tri%20Opt/%22%3E%3C[PERSISTENT SCRIPT CODE INJECT VIA PATH%22%29%20%3C">
"​​​​​><[PERSISTENT SCRIPT CODE EXECUTION!]' <<="" a=""> / </span></div>


The vulnerability can be fixed by parsing the secound input request of the file upload function next to the display of the myresource listing.
To fix the issue completly it is also required to parse the path url request which allows to include but not execute the context.

2012-07-14: Vendor Fix/Patch by Barracuda Networks

The security risk of the input validation filter bypass vulnerability is estimated as high(-).

Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm@vulnerability-lab.com)

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-
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profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such damages. Some
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may not apply. We do not approve or encourage anybody to break any vendor licenses, policies, deface websites, hack into databases
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Copyright © 2012 | Vulnerability Laboratory

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