The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
Low
C
There is some impact on confidentiality, but the attacker either does not gain control of any data, or the information obtained does not have a significant impact on the system or its operations.
Integrity
Low
I
Modification of data is possible, but the attacker does not have control over what can be modified, or the extent of what the attacker can affect is limited. The data modified does not have a direct, serious impact on the system.
Availability
None
A
There is no impact on the availability of the system; the attacker does not have the ability to disrupt access to or use of the system.
Title:
======
Barracuda Appliances - Validation Filter Bypass Vulnerability
Date:
=====
2012-07-16
References:
===========
http://www.vulnerability-lab.com/get_content.php?id=661
VL-ID:
=====
661
Common Vulnerability Scoring System:
====================================
5.5
Abstract:
=========
The Vulnerability Laboratory Research Team discovered a input validation filter bypass vulnerability in Barracudas Network appliance products.
Report-Timeline:
================
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
Status:
========
Published
Exploitation-Technique:
=======================
Remote
Severity:
=========
High
Details:
========
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=
false&sortName=fileSystem.size&
amp;amp;actionTarget=list" class="columnHeader">Size</a>
</td>
... 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&
launchId=l7e68d5&path=smb/Sales%20Folder/
Testing%20from%20Tri%20Opt/%22%3E%3C[PERSISTENT SCRIPT CODE INJECT VIA PATH%22%29%20%3C">
"><[PERSISTENT SCRIPT CODE EXECUTION!]' <<="" a=""> / </span></div>
Reference(s):
../video-poc.wmv
Solution:
=========
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
Risk:
=====
The security risk of the input validation filter bypass vulnerability is estimated as high(-).
Credits:
========
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected])
Disclaimer:
===========
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