CVE-2019-16976 in FusionPBX
Summary
by MITRE
In FusionPBX up to 4.5.7, the file app\destinations\destination_imports.php uses an unsanitized "query_string" variable coming from the URL, which is reflected on 2 occasions in HTML, leading to XSS.
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Analysis
by VulDB Data Team • 01/27/2024
The vulnerability CVE-2019-16976 represents a cross-site scripting flaw in FusionPBX version 4.5.7 and earlier, where the application fails to properly sanitize user input from URL parameters. This issue specifically affects the destination_imports.php file within the application's destinations module, making it a critical security concern for organizations relying on this telephony management platform. The vulnerability stems from improper input validation and output encoding practices that allow malicious actors to inject malicious scripts into the application's response.
The technical flaw manifests through the unsanitized "query_string" parameter that originates from URL requests and is subsequently reflected in HTML output twice within the destination_imports.php script. This unvalidated input flows directly into the application's response without proper HTML escaping or sanitization, creating a classic XSS attack vector. When a victim visits a maliciously crafted URL containing script payloads, the browser executes these scripts within the context of the vulnerable FusionPBX application, potentially compromising user sessions and enabling further attacks. The vulnerability aligns with CWE-79 which categorizes cross-site scripting as a weakness where applications fail to properly validate or escape user-supplied data before including it in web pages.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to hijack user sessions, steal sensitive authentication tokens, and potentially gain unauthorized access to the telephony system. An attacker could craft malicious URLs that redirect users to phishing pages or inject malicious code that captures user credentials and system information. The reflected nature of this XSS vulnerability means that the attack requires user interaction through a malicious link, but once clicked, it can execute in the context of the authenticated user's session. This vulnerability particularly affects organizations using FusionPBX for VoIP management, where unauthorized access could lead to complete compromise of communication infrastructure.
Mitigation strategies for CVE-2019-16976 should prioritize immediate patching of the FusionPBX application to version 4.5.8 or later, which contains the necessary fixes for this vulnerability. Organizations should implement proper input validation and output encoding practices throughout their web applications, ensuring that all user-supplied data is sanitized before being incorporated into HTML responses. The implementation of Content Security Policy headers can provide additional protection against XSS attacks by restricting script execution within the application context. Security teams should also conduct regular vulnerability assessments and input validation testing to identify similar issues in other components of their telephony and web infrastructure. This vulnerability demonstrates the importance of following secure coding practices as outlined in the OWASP Top Ten and ATT&CK framework's T1203 technique for exploiting web application vulnerabilities, emphasizing the need for comprehensive security controls in telecommunications management systems.