CVE-2021-37441 in Axon PBX
Summary
by MITRE • 07/26/2021
NCH Axon PBX v2.22 and earlier allows path traversal for file deletion via the logdelete?file=/.. substring.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/28/2021
The vulnerability CVE-2021-37441 affects NCH Axon PBX versions 2.22 and earlier, representing a critical path traversal flaw that enables unauthorized file deletion operations. This vulnerability resides within the web interface of the PBX system and specifically targets the logdelete functionality where users can specify file paths for deletion. The issue stems from inadequate input validation and sanitization of the file parameter in the logdelete?file=/.. URL substring, allowing malicious actors to manipulate the file path and potentially access or delete files outside the intended directory structure.
The technical implementation of this vulnerability exploits the absence of proper path validation mechanisms within the PBX application's file deletion process. When the system receives a request containing the logdelete?file=/.. parameter, it fails to properly sanitize or restrict the file path, enabling attackers to traverse directories using the ../ sequence. This path traversal capability extends beyond simple file access to include deletion operations, creating a severe privilege escalation vector. The vulnerability is particularly dangerous because it operates at the application level and does not require authentication to exploit, making it accessible to anyone who can interact with the web interface.
From an operational impact perspective, this vulnerability presents significant risks to organizations relying on NCH Axon PBX systems for their telephony infrastructure. Attackers could potentially delete critical log files, system configuration data, or even executable components that could lead to service disruption or complete system compromise. The ability to traverse file paths and delete arbitrary files creates opportunities for persistent attacks where malicious actors might target system stability, data integrity, or availability. The vulnerability also increases the attack surface for other potential exploits, as compromised systems could be used as launching points for further attacks within the network infrastructure.
Organizations should immediately implement mitigations including applying the vendor-provided patches or updates that address the path traversal vulnerability in the logdelete functionality. Network segmentation and access controls should be enhanced to limit exposure of the PBX web interface to untrusted networks. The implementation of web application firewalls and input validation rules can help prevent exploitation attempts by blocking suspicious path traversal sequences. Additionally, regular security assessments should be conducted to identify similar vulnerabilities in other components of the telephony infrastructure. This vulnerability aligns with CWE-22 Path Traversal and maps to ATT&CK technique T1059 Command and Scripting Interpreter, as exploitation may involve executing commands through the compromised PBX interface. Organizations should also consider implementing comprehensive logging and monitoring of file system operations to detect potential exploitation attempts and maintain audit trails for security incident response.