Barracuda Cloud Series - Filter Bypass Vulnerability (ID 731)

CVE Category Price Severity
CVE-2021-20301 CWE-200 Not specified High
Author Risk Exploitation Type Date
Eren Shay High Remote 2015-02-12
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L 0.02192 0.50148

CVSS vector description

Our sensors found this exploit at:

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Document Title:
Barracuda Cloud Series - Filter Bypass Vulnerability (ID 731)

References (Source):

Barracuda Networks Security ID (BNSEC): 731

Release Date:

Vulnerability Laboratory ID (VL-ID):

Common Vulnerability Scoring System:

Abstract Advisory Information:
The Vulnerability Laboratory Research Team discovered a filter bypass vulnerability in the official Barracuda Cloud Series Products.

Vulnerability Disclosure Timeline:
2015-01-19:     Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Affected Product(s):
Barracuda Networks
Product: Cloud Control Center 2014 Q2

Exploitation Technique:

Severity Level:

Technical Details & Description:
A filter bypass vulnerability has been discovered in the official Barracuda Networks Cloud Series Appliance Applications 2014-Q1. The filter bypass issue allows an attacker to bypass the secure filter validation of the service to execute malicious script codes.

The barracuda filter blocks for example standard iframes, scripts and other invalid code context: The cloud service has a own exception-handling to parse or encode malicious injected web context. The mechanism filters the first request and sanitizes the output in every input field.

During a pentest we injected a standard iframe to check and provoke the validation. The frame got blocked! In the next step the attacker splits (%20%20%20) the request and injects at the end an onload frame to an external malicious source. The second iframe with the onload alert executes the script codes after the validation encoded only the first script code tag. The second script code tag can bypass the applicance filter mechanism and executes in the web context of affected modules. The secure validation does not recognize a splitted request which results in client-side and application-side script code execution in
the cloud series products.

The security risk of the filter bypass vulnerability is estimated as medium and the cvss (common vulnerability scoring system) count is 4.1 (medium).
Exploitation of the filter bypass vulnerability requires a low privileged application user account with restricted access and low user interaction.
Successful exploitation of the vulnerability results in session hijacking, persistent phishing, persistent external redirects and persistent manipulation
of affected or connected module context.

Vulnerable Request Method(s):
                                [+] POST & GET

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

<iframe src=a>%20%20%20%20\"><iframe src= onload=alert("VL") <

<script language=JavaScript>m='%3Ciframe%20src%3Da%3E%2520%2520%2520%2520%5C%22%3E%3Ciframe%20src%3Dhttp%3A//';d=unescape(m);document.write(d);</script>

Solution - Fix & Patch:
The issue can be patched by a secure validation of the full message input body context of any input or request method attempt. Ensure that the validaton does not only encode the first injected script code since a empty char arrives. Filter all web context that runs through the requesting procedure and parse separatly to prevent script code injection attacks.

Note: Barracuda Networks patched the vulnerability and acknowledged the researcher. Updates are available in Barracuda Labs and the Customer Service.

Security Risk:
The security risk of the filter bypass web vulnerability in the barracuda cloud product series is estimated as medium. (CVSS 4.1)

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

Disclaimer & Information:
The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all warranties, either expressed or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability-Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss of business profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. We do not approve or encourage anybody to break any vendor licenses, policies, deface websites, hack into databases or trade with fraud/stolen material.

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