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Subject: Barracuda Networks Web Security Flex Appliance Application v4.x - Filter Bypass & Persistent Vulnera
From: Vulnerability Lab <research () vulnerability-lab ! com>
Date: 2014-08-25 15:33:48
Message-ID: 53FB575C.1010405 () vulnerability-lab ! com
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Document Title:
===============
Barracuda Networks Web Security Flex Appliance Application v4.x - Filter Bypass & \
Persistent Vulnerabilities (BNSEC 707)
References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=749
Barracuda Networks Security ID (BNSEC): 707
Video: http://www.vulnerability-lab.com/get_content.php?id=1205
View Video: http://www.youtube.com/watch?v=1D9PS4bW8VM
Release Date:
=============
2014-08-20
Vulnerability Laboratory ID (VL-ID):
====================================
749
Common Vulnerability Scoring System:
====================================
3.8
Product & Service Introduction:
===============================
The Barracuda Web Security Service is a cloud-based web filtering service ideal for \
organizations with users in multiple locations. With no hardware to install, this \
powerful SaaS web filter quickly and affordably lets administrators safeguard users \
against aggressive malware while centrally managing user access to web content, \
applications, media, file types and more. It even extends content security and \
management to off-network mobile devices – perfect for schools that issue iPads to \
students, or any organization that relies on mobility.
As an enterprise-grade solution for web security, Barracuda Web Security Service \
saves administrators time otherwise spent disinfecting computers and dealing with \
data breaches. Barracuda Web Security Service's intuitive web UI gives clear \
visibility into web activity which speeds network troubleshooting and policy \
management. Interactive graphs let administrators drill down from high-level \
overviews of the organization's web activity to fine-grained information about users, \
websites, applications, files, bandwidth and other factors effecting performance and \
user productivity. Reporting is just as convenient and granular with no database \
administration required. Built on a massively scalable worldwide multi-tenant \
architecture that provides advanced web filtering to customers in fifty countries, \
Barracuda Web Security Service delivers the fastest, most reliable web filtering in \
the industry.
(Copy of the Vendor Homepage: \
https://www.barracudanetworks.com/products/websecurityflex )
Abstract Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered multiple web vulnerabilities in \
the official Barracuda Networks Security Flex v4.1 Appliance Web-Application.
Vulnerability Disclosure Timeline:
==================================
2013-11-09: Researcher Notification & Coordination (Benjamin Kunz Mejri)
2013-11-10: Vendor Notification (Barracuda Networks - Bug Bounty Team)
2013-11-13: Vendor Response/Feedback (Barracuda Networks - Bug Bounty Team)
2014-08-10: Vendor Fix/Patch Notification (Barracuda Networks - Developer Team)
2014-08-20: Public Disclosure (Vulnerability Laboratory)
Discovery Status:
=================
Published
Affected Product(s):
====================
Barracuda Networks
Product: Web Security Flex 4.1
Exploitation Technique:
=======================
Remote
Severity Level:
===============
Medium
Technical Details & Description:
================================
Multiple persistent input validation vulnerabilities are detected in the official \
Barracuda Networks Security Flex v4.1 Application Service. The bugs allow remote \
attackers to implement/inject malicious script code on the application side \
(persistent) of the vulnerable module.
The persistent vulnerabilities are located in the bypass_password and shared_secret \
parameters of the `Remote Filtering > Safe Browser > Provisioning` module. The \
attacker is able to bypass the `shared password/secret` input field validation to \
manipulate the input field context. The script code execution occurs after the \
attacker clicked the `shared secret` information show/hide button in the \
`Provisioning` service module. The attack method is located on the application-side \
of the service and the request method to inject the payload is POST.
To bypass the input field validation and execute the earlier injected string via \
POST, it is required to split (%20) the payload. During the pentests we revealed \
that script code executions (html,js & php) are possible. The input of the validation \
is broken and through the reverse function `hide/show` it is possible to manipulate \
the application context or capture the input.
The security risk of the persistent vulnerabilities are estimated as medium with a \
cvss (common vulnerability scoring system) count of 3.8. Exploitation requires low \
user inter action and a registered low privileged web application user account. \
Successful exploitation of the vulnerability results in session hijacking \
(manager/admin), persistent phishing, persistent external redirects or persistent \
manipulation of affected or connected module context.
Request Method(s):
[+] POST
Vulnerable Service(s):
[+] Web Security Flex
Vulnerable Module(s):
[+] Remote Filtering > Safe Browser > Provisioning
Vulnerable Function(s):
[+] hide input
[+] show input (reverse)
Vulnerable Parameter(s):
[+] bypass_password
[+] shared_secret
Affected Module(s):
[+] Provisioning
Proof of Concept (PoC):
=======================
The persistent web vulnerabilities can be exploited by remote attackers and local low \
privileged user accounts 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: String (Bypass %20)
%20<iframe%20src=a>%20%20%20%20\"><iframe src=a onload=alert(\"VL\") <
PoC: (Context Show & Hide Function) [bypass_password & shared_secret]
<div class=\"field\">
<label class=\"label\" for=\"bypass_password\">Bypass Password:</label>
<input name=\"bypass_password\" id=\"bypass_password\" value=\"northhigh\" \
type=\"password\">​​​​​ <small \
onclick=\"$(\'#bypass_password_ct\').show().find(\'strong\').html($(\'#bypass_password\').val())\" \
class=\"link2\">show</small> <span class=\"info\" id=\"bypass_password_ct\" \
style=\"\"> <br> Password: \"
<strong>\%20"><[PERSISTENT INJECTED SCRIPT CODE!]\%20"><[PERSISTENT INJECTED SCRIPT \
CODE!]\") <\%20"><[PERSISTENT INJECTED SCRIPT CODE!]\") <\%20"><[PERSISTENT INJECTED \
SCRIPT CODE!]\") <\") \
<northhigh</iframe>​​​​​</strong>\" — <span \
class=\"link2\" onclick=\"$(this.parentNode).hide()\">hide</span></span> \
</div>
--- POC Session Logs (MANIPULATED TO BYPASS) [POST] ---
auth_scheme=none
session_timeout=0
idle_timeout=0
shared_secret=%20%3C[PERSISTENT INJECTED SCRIPT CODE!]%3Da%3E%2520%2520
bypass_password=%20%3C[PERSISTENT INJECTED SCRIPT \
CODE!]%3Da%3E%2520%2520%2520%2520%22%3E%3C[PERSISTENT INJECTED SCRIPT \
CODE!]%3Da+onload%3Dalert(%22VL%22)+%3C bypass_filter=192.168.*%3B10.10.*%3B172.16.*
fail_open=1
enable_geolocation=1
allow_temp_disable=1
allow_stop=1=
is_ajax=1
ajax_response_format=json
Reference(s):
https://wsf.127.0.0.1:1338/r/mobile
Solution - Fix & Patch:
=======================
The issue can be fixed by a secure parse and encode of the vulnerable parameter in \
the Provisioning module. Restrict and filter the vulnerable `bypass_password` and \
`shared_secret` values to prevent further exploitation by script code injection \
attacks.
Security Risk:
==============
The security risk of the persistent web vulnerabilities are estimated as medium.
Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri \
(bkm@evolution-sec.com) [www.vulnerability-lab.com]
Disclaimer & Information:
=========================
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