CVE-2018-5700 in Server
Summary
by MITRE
Winmail Server through 6.2 allows remote code execution by authenticated users who leverage directory traversal in a netdisk.php copy_folder_file call (in inc/class.ftpfolder.php) to move a .php file from the FTP folder into a web folder.
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Analysis
by VulDB Data Team • 12/23/2019
The vulnerability identified as CVE-2018-5700 affects Winmail Server versions through 6.2 and represents a critical remote code execution flaw that can be exploited by authenticated users. This vulnerability stems from improper input validation within the server's file handling mechanisms, specifically in the netdisk.php component that processes folder and file operations. The flaw exists in the inc/class.ftpfolder.php file where the copy_folder_file function fails to properly sanitize user-supplied paths, creating an opportunity for directory traversal attacks. Attackers who have gained authentication access to the server can leverage this vulnerability to escalate their privileges and execute arbitrary code on the target system.
The technical implementation of this vulnerability involves a directory traversal attack that exploits the lack of proper path validation in the FTP to web folder transfer functionality. When an authenticated user makes a request to copy a file using the copy_folder_file function, the system does not adequately validate or sanitize the destination path, allowing attackers to manipulate the file transfer operation. This manipulation enables the movement of a .php file from an FTP accessible directory into a web-accessible directory where it can be executed as a web script. The vulnerability specifically targets the server's file management capabilities and demonstrates a classic path traversal flaw that has been documented in various security frameworks including CWE-22 which categorizes improper limitation of a pathname to a restricted directory.
The operational impact of CVE-2018-5700 is severe and can result in complete system compromise when exploited. Once an attacker successfully executes this attack, they gain the ability to run arbitrary code with the privileges of the web server process, potentially leading to data theft, system infiltration, or further network compromise. The vulnerability is particularly dangerous because it requires only authenticated access, meaning that attackers who have obtained valid user credentials can exploit this flaw without requiring additional privileges or complex attack vectors. This makes the vulnerability especially concerning for environments where user accounts may be compromised through social engineering, credential theft, or other means. The attack can be executed through standard web-based interfaces, making it accessible to attackers with basic technical knowledge and reducing the barrier to successful exploitation.
Mitigation strategies for CVE-2018-5700 should include immediate patching of affected Winmail Server installations to version 6.3 or later, which contains the necessary security fixes. Organizations should also implement network segmentation to limit access to the Winmail Server and restrict authentication access to only necessary personnel. Additional defensive measures include implementing web application firewalls to monitor and filter suspicious file transfer requests, conducting regular security audits of file handling operations, and establishing strict access controls for FTP and web folders. The vulnerability aligns with ATT&CK technique T1059 which covers command and scripting interpreter usage, and represents a common attack pattern where legitimate system functionality is abused to achieve unauthorized code execution. Regular security monitoring should focus on unusual file transfer activities and unauthorized modifications to web-accessible directories to detect potential exploitation attempts.