CVE-2019-16977 in FusionPBX
Summary
by MITRE
In FusionPBX up to 4.5.7, the file app\extensions\extension_imports.php uses an unsanitized "query_string" variable coming from the URL, which is reflected in HTML, leading to XSS.
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Analysis
by VulDB Data Team • 01/27/2024
The vulnerability identified as CVE-2019-16977 affects FusionPBX versions up to 4.5.7 and represents a critical cross-site scripting flaw in the extension import functionality. This vulnerability resides within the file app/extensions/extension_imports.php where the application fails to properly sanitize user-supplied input originating from the query_string parameter in HTTP requests. The unsanitized input is subsequently reflected back in the HTML response without adequate encoding or validation measures, creating an exploitable condition that allows malicious actors to inject arbitrary script code into web pages viewed by unsuspecting users.
The technical implementation of this vulnerability demonstrates a classic reflected cross-site scripting pattern where the application directly incorporates user input into its output without proper sanitization or output encoding. When a user visits a maliciously crafted URL containing malicious script code within the query_string parameter, the application processes this input and reflects it back in the HTML response. This creates an environment where attackers can execute malicious scripts in the context of the victim's browser session, potentially leading to session hijacking, credential theft, or unauthorized actions within the application.
From an operational impact perspective, this vulnerability poses significant risks to FusionPBX deployments as it allows attackers to exploit the system through social engineering campaigns or by tricking users into clicking malicious links. The reflected nature of the vulnerability means that the attack vector is typically delivered through phishing emails, compromised websites, or malicious links shared in communication channels. Successful exploitation could enable attackers to steal administrative credentials, modify extension configurations, or gain unauthorized access to the telephony system's administrative interface, potentially compromising the entire communication infrastructure.
The vulnerability aligns with CWE-79, which specifically addresses Cross-site Scripting flaws in web applications, and maps to ATT&CK technique T1566 for initial access through spearphishing or malicious links. Organizations using FusionPBX versions prior to 4.5.8 should immediately implement mitigations including input validation and output encoding mechanisms to prevent the reflection of unsanitized user input. The recommended approach involves implementing proper parameter validation, sanitizing all user-supplied input, and applying appropriate HTML encoding to prevent script execution in the browser context. Additionally, organizations should consider implementing content security policies to further mitigate the impact of potential XSS attacks and ensure that all user input is properly validated before being processed or displayed in web responses.
This vulnerability represents a critical security gap that directly impacts the integrity and confidentiality of telephony system management interfaces, emphasizing the importance of proper input validation and output encoding practices in web application development. The flaw demonstrates how seemingly simple input handling can create significant security implications when proper sanitization measures are not implemented, highlighting the need for comprehensive security testing and code review processes in telecommunications software development.