CVE-2018-6409 in Machform
Summary
by MITRE
An issue was discovered in Appnitro MachForm before 4.2.3. The module in charge of serving stored files gets the path from the database. Modifying the name of the file to serve on the corresponding ap_form table leads to a path traversal vulnerability via the download.php q parameter.
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Analysis
by VulDB Data Team • 07/13/2025
The vulnerability identified as CVE-2018-6409 affects Appnitro MachForm versions prior to 4.2.3, representing a critical path traversal flaw that directly impacts the application's file serving mechanism. This vulnerability stems from the application's improper handling of file paths retrieved from its database, specifically within the ap_form table structure. The flaw manifests when attackers manipulate the filename stored in the database to include directory traversal sequences, allowing them to access files outside the intended directory structure.
The technical implementation of this vulnerability occurs through the download.php script's q parameter, which serves as the primary entry point for file retrieval operations. When the application processes requests for stored files, it retrieves the file path information from the database and uses it directly in file operations without proper validation or sanitization. This design flaw creates a direct path traversal condition where maliciously crafted filenames can manipulate the file system access routines to navigate to arbitrary locations on the server.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as it provides attackers with the capability to potentially read sensitive system files, configuration data, or other critical resources stored on the server. Attackers can exploit this weakness to bypass normal access controls and retrieve files that should remain protected, including database credentials, application configuration files, or even system-level information that could aid in further exploitation. The vulnerability essentially allows attackers to traverse the file system hierarchy and access files that are not intended to be publicly available through the normal application interface.
This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The flaw demonstrates poor input validation practices and highlights the importance of implementing proper path sanitization when dealing with user-controllable data that influences file system operations. From an attacker's perspective, this vulnerability maps to multiple ATT&CK techniques including T1083 (File and Directory Discovery) and T1566 (Phishing with Malicious Attachments), as it enables unauthorized access to sensitive files that could be used for privilege escalation or data exfiltration.
The recommended mitigation strategy involves implementing comprehensive input validation and sanitization for all user-controllable parameters that influence file system operations. Organizations should ensure that the application performs strict validation of file paths retrieved from the database, implementing proper path normalization and restriction mechanisms that prevent traversal sequences from being processed. Additionally, the application should enforce strict file access controls and implement proper directory restrictions that limit file system access to only intended directories. The vendor has addressed this issue in version 4.2.3 through improved input validation and path handling mechanisms that prevent malicious path traversal attempts.