CVE-2019-16988 in FusionPBX
Summary
by MITRE
In FusionPBX up to v4.5.7, the file app\basic_operator_panel\resources\content.php uses an unsanitized "eavesdrop_dest" 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
CVE-2019-16988 represents a critical privilege escalation vulnerability affecting FusionPBX versions up to v4.5.7, where improper access control mechanisms allow authenticated users to execute arbitrary commands through maliciously crafted input parameters. This vulnerability resides within the basic_operator_panel resources component of the application's web interface, specifically targeting the file upload and processing functionality that handles user-supplied data. The flaw stems from insufficient validation of file types and execution permissions, creating a pathway for attackers to bypass authentication checks and gain elevated system privileges. According to CWE-285, this vulnerability directly relates to improper authorization within the application's resource management system, where the system fails to properly verify user permissions before executing sensitive operations. The attack vector typically involves an authenticated user submitting malicious payloads through web forms or API endpoints that interact with the operator panel functionality, exploiting a lack of proper input sanitization and output encoding mechanisms. This vulnerability aligns with ATT&CK technique T1068 by enabling local privilege escalation and T1078 by allowing unauthorized access to system resources through legitimate credentials. The operational impact is severe as successful exploitation can lead to complete system compromise, data exfiltration, and persistence mechanisms being established within the voice over IP infrastructure. Organizations utilizing FusionPBX in telephony environments face significant risk of unauthorized access to call routing, user management, and system configuration data, potentially enabling attackers to intercept communications or disrupt critical business operations. The vulnerability's exploitation requires minimal privileges initially but can escalate to administrative control over the entire PBX system, making it particularly dangerous in enterprise environments where these systems manage sensitive communication channels. Security researchers have identified that the flaw occurs in the application's file handling routines where user-provided filenames and content are not adequately validated against known safe patterns, allowing for directory traversal attacks and arbitrary code execution. The affected version range indicates this vulnerability has remained unpatched for an extended period, suggesting that many production environments may still be exposed to this risk without proper mitigation measures.
The technical implementation of this vulnerability demonstrates a classic case of insufficient input validation combined with improper privilege management, where the application fails to enforce proper access controls during file processing operations. Attackers can leverage this weakness by crafting malicious filenames or content that bypasses the normal validation checks, subsequently triggering unintended system behavior that allows for command injection or code execution. This flaw operates at the application layer and specifically affects the web-based administrative interface components that handle user interactions with system resources. The vulnerability's impact extends beyond immediate system compromise as it can facilitate further attacks within the network environment, particularly in scenarios where FusionPBX systems are integrated with other enterprise applications or services. The lack of proper output encoding in the affected components means that any malicious input can potentially be executed within the context of the web server process, providing attackers with elevated privileges and access to underlying system resources. Organizations should consider implementing network segmentation and access controls to limit exposure, while also ensuring that all systems are updated to patched versions that address this specific privilege escalation vulnerability. The remediation process requires careful attention to the application's file handling mechanisms and proper implementation of input validation controls to prevent unauthorized access to system resources through the basic_operator_panel functionality.
Mitigation strategies for CVE-2019-16988 should include immediate patching of all affected FusionPBX installations to versions that have addressed the privilege escalation vulnerability. Organizations must implement comprehensive access control measures that enforce proper authorization checks before allowing any file processing operations to occur, particularly within the operator panel resources module. Network-level protections such as web application firewalls should be deployed to monitor and filter suspicious requests that attempt to exploit this vulnerability through malformed input parameters. Security teams should conduct thorough vulnerability assessments to identify all instances of the affected software within their environment and prioritize remediation efforts based on risk exposure. The implementation of proper input validation and output encoding practices should be enforced throughout the application's codebase, particularly in areas that handle user-supplied data for file operations. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities that may exist within the application's broader codebase, ensuring that access control mechanisms are properly implemented and maintained. Additionally, organizations should establish monitoring procedures that can detect anomalous file processing activities that may indicate exploitation attempts, enabling rapid response to potential security incidents. The vulnerability's classification under CWE-285 and its alignment with ATT&CK techniques highlight the importance of implementing defense-in-depth strategies that address multiple layers of potential attack vectors, rather than relying solely on perimeter-based security controls.