Barracuda Networks Web Security Flex 4.1 Persistent Vulnerabilities

CVE Category Price Severity
CVE-2021-29900 CWE-79 $5,000 High
Author Risk Exploitation Type Date
Unknown High Remote 2014-08-26
CVSS:4.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H 0.9 0.998

CVSS vector description

Our sensors found this exploit at:

Below is a copy:

Document Title:
Barracuda Networks Web Security Flex v4.1 - Persistent Vulnerabilities (BNSEC-699)

References (Source):


Release Date:

Vulnerability Laboratory ID (VL-ID):

Common Vulnerability Scoring System:

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: )

Abstract Advisory Information:
The Vulnerability Laboratory Research Team discovered a web vulnerability in the official Barracuda Networks Web Security Flex v4.1 Application Service.

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:

Affected Product(s):
Barracuda Networks
Product: Web Security Flex 4.1

Exploitation Technique:

Severity Level:

Technical Details & Description:
A persistent input validation vulnerability has been discovered in the official Barracuda Networks Security Flex v4.1 Application Web-Application.
The bug allows remote attackers to inject own malicious script codes in the vulnerable module on the application-side of the appliance service. 

The persistent vulnerability is located in the vulnerable Domain Alias, LDAP Host and Bind DN/Username values of the `Remote Filtering > Authentication 
> Add Authentication Server` module. Low privileged user accounts are able to inject via POST method request own malicious script codes to compromise 
the appliance web-application service. The attack vector is located on the application-side and the request method to inject malicious conext is POST.

The security risk of the persistent vulnerabilities are estimated as medium with a cvss (common vulnerability scoring system) count of 4.0.
Exploitation of the security issue requires low user inter action (view listing) & a registered low privileged web application user account.
Successful exploitation of the security vulnerability results in session hijacking (manager/admin) or stable (persistent) context manipulation.

Request Method(s):
[+] POST

Vulnerable Service(s):
[+] Web Security Flex

Vulnerable Module(s):
[+] Remote Filtering > Authentication > Add Authentication Server > TEST SETTINGS or SAVE + Listing!

Vulnerable Parameter(s):
[+] Domain Alias
[+] LDAP Host
[+] Bind DN/Username

Proof of Concept (PoC):
The persistent web vulnerability in the exception-handling can be exploited by remote attackers with low privileged user account and low required user inter action. 
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.

Review: Domain Alias, LDAP Host and Bind DN/Username

<div class="form-result form-result-error" id="flex-global-form-result" 
style="display: block;">Unable to connect to​​​​​ ">​​​​​<iframe src="a">%20%20%20%20"><[PERSISTENT SCRIPT CODE INJECTION!]") <:389</iframe></div>

POST REQUEST (BLOCKED): Exception-Handling


PoC: String (Bypass %20)
">Unable to connect to​​​​​ ">​​​​​<iframe src="a">%20%20%20%20"><iframe onload=alert("VL") <


Solution - Fix & Patch:
The vulnerability can be patched by a secure parse and encode of all invalid context exception-handling messages values. 
Disallow to redisplay the insecure input and filter wrong exception to prevent execution of persistent codes in the context of the security appliance application.

Security Risk:
The security risk of the persistent exception-handling validation web vulnerability is estimated as medium.

Credits & Authors:
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected]) []

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