CVE-2017-9846 in Server
Summary
by MITRE
Winmail Server 6.1 allows remote code execution by authenticated users who leverage directory traversal in a netdisk.php move_folder_file call to move a .php file from the FTP folder into a web folder.
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Analysis
by VulDB Data Team • 10/20/2019
The vulnerability identified as CVE-2017-9846 represents a critical remote code execution flaw in Winmail Server version 6.1 that demonstrates a classic directory traversal weakness combined with insufficient input validation. This vulnerability exists within the netdisk.php component of the email server software, specifically in the move_folder_file function that handles file operations between different storage locations. The flaw enables authenticated users to manipulate file paths and move malicious PHP files from FTP directories into web-accessible folders, creating a direct pathway for arbitrary code execution on the server.
The technical exploitation of this vulnerability relies on the server's failure to properly validate and sanitize user-supplied file paths during directory traversal operations. When an authenticated user invokes the move_folder_file function in netdisk.php, the application does not adequately filter or sanitize the input parameters that define source and destination paths. This allows attackers to craft malicious path sequences that bypass normal directory restrictions and place executable PHP code in web root directories where it can be executed by the web server. The vulnerability is particularly dangerous because it requires only authentication access, which many organizations may not adequately restrict or monitor.
From an operational impact perspective, this vulnerability provides attackers with a straightforward path to compromise entire server infrastructures. Once successful exploitation occurs, attackers can execute arbitrary commands with the privileges of the web server process, potentially leading to complete system compromise, data exfiltration, or use as a foothold for further lateral movement within the network. The vulnerability affects organizations using Winmail Server 6.1, which was widely deployed in enterprise environments for email and file sharing services, making it a significant target for threat actors seeking persistent access to corporate networks. The impact extends beyond immediate code execution to include potential data loss, service disruption, and regulatory compliance violations.
Organizations should implement multiple layers of mitigation strategies to address this vulnerability effectively. Immediate remediation requires applying the vendor-provided security patches or upgrading to newer versions of Winmail Server that address the directory traversal flaw. Network segmentation and access control measures should be strengthened to limit the scope of authenticated access, particularly restricting file manipulation capabilities to only essential administrative users. Input validation and sanitization should be implemented at multiple levels including application firewalls, web application firewalls, and server-side code modifications to prevent path traversal attacks. The vulnerability aligns with CWE-22 Directory Traversal and follows patterns commonly associated with ATT&CK technique T1059 Command and Scripting Interpreter, where adversaries leverage legitimate system tools and processes to execute malicious code. Regular security audits and penetration testing should include validation of file operation functions to identify similar path traversal vulnerabilities in other applications and systems within the organization's infrastructure.