CVE-2019-16971 in FusionPBX
Summary
by MITRE
In FusionPBX up to 4.5.7, the file app\messages\messages_thread.php uses an unsanitized "contact_uuid" variable coming from the URL, which is reflected on 3 occasions in HTML, leading to XSS.
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Analysis
by VulDB Data Team • 01/17/2024
The vulnerability identified as CVE-2019-16971 affects FusionPBX versions up to 4.5.7 and represents a classic cross-site scripting vulnerability that exploits improper input validation within the application's message handling functionality. This issue resides in the app/messages/messages_thread.php file where the application fails to properly sanitize the contact_uuid parameter obtained from HTTP request parameters. The flaw demonstrates a clear breakdown in the application's security input validation mechanisms, allowing malicious actors to inject arbitrary HTML content through the URL parameter that gets subsequently reflected in the application's user interface without adequate sanitization or encoding.
The technical implementation of this vulnerability occurs through the improper handling of user-supplied data within the web application's rendering pipeline. When a user navigates to a page containing the vulnerable contact_uuid parameter, the application directly incorporates this unsanitized input into HTML output contexts where it is subsequently rendered in the browser. This creates three distinct reflection points within the HTML output where malicious scripts can be executed in the context of other users' browsers who access the affected page. The vulnerability type aligns with CWE-79 which specifically addresses Cross-Site Scripting flaws in web applications, where insufficient validation or sanitization of input data leads to the execution of malicious scripts.
The operational impact of this vulnerability extends beyond simple data theft or session hijacking, as it enables attackers to perform a range of malicious activities including but not limited to credential theft, session manipulation, and redirection to malicious sites. An attacker could craft a malicious URL containing script code within the contact_uuid parameter and send it to a victim user, potentially compromising their session or gaining unauthorized access to their account. This vulnerability is particularly concerning in the context of FusionPBX, which is a telephony management system that often handles sensitive communication data and user credentials, making it a prime target for exploitation.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and output encoding mechanisms. The most effective immediate fix involves sanitizing all user-supplied input parameters before they are processed or rendered in HTML contexts. This can be achieved through the implementation of proper HTML encoding functions that convert special characters into their HTML entity equivalents, preventing script execution in the browser. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against XSS attacks by restricting the sources from which scripts can be loaded. Organizations should also consider implementing a comprehensive input validation framework that enforces strict data type checking and sanitization for all parameters received from external sources, aligning with security best practices outlined in the OWASP Top Ten and NIST cybersecurity guidelines. The vulnerability demonstrates the critical importance of implementing defense-in-depth strategies that include both input validation and output encoding to prevent XSS exploitation across all application components.