CVE-2009-3643 in XM Easy Personal FTP Server
Summary
by MITRE
Dxmsoft XM Easy Personal FTP Server 5.8.0 allows remote attackers to cause a denial of service via a long argument to the (1) LIST and (2) NLST commands, a differnt issue than CVE-2008-5626 and CVE-2006-5728.
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Analysis
by VulDB Data Team • 10/14/2025
The vulnerability identified as CVE-2009-3643 affects Dxmsoft XM Easy Personal FTP Server version 5.8.0 and represents a denial of service weakness that can be exploited by remote attackers through carefully crafted input to specific FTP commands. This vulnerability specifically targets the LIST and NLST commands within the FTP server implementation, creating a scenario where malicious input can disrupt normal server operations. The issue is distinct from previously identified vulnerabilities such as CVE-2008-5626 and CVE-2006-5728, indicating it represents a unique code flaw rather than a recurring pattern of weaknesses in the software's FTP implementation. The vulnerability falls under the category of buffer overflow conditions and input validation failures that are commonly classified under CWE-121 and CWE-125 in the Common Weakness Enumeration framework, which deals with buffer overflow conditions and improper input validation.
The technical flaw manifests when the FTP server processes LIST and NLST commands with excessively long arguments that exceed the server's expected input length limits. These commands are fundamental to FTP operations as they allow clients to list directory contents and retrieve file names respectively. When an attacker sends a malformed argument that surpasses the server's internal buffer capacity or processing limits, the server fails to handle the input gracefully and instead crashes or becomes unresponsive. This occurs because the server lacks proper input length validation and robust error handling mechanisms for these specific commands. The vulnerability is particularly concerning as it can be exploited remotely without requiring authentication, making it accessible to any attacker with network access to the FTP server.
The operational impact of this vulnerability extends beyond simple service disruption as it can lead to complete server unavailability and potential data access interruptions for legitimate users. When the server crashes or becomes unresponsive due to the denial of service attack, legitimate FTP clients lose access to file transfer capabilities, which can severely impact business operations that depend on file sharing and data management. The vulnerability affects the availability aspect of the CIA triad by compromising the system's ability to provide continuous service to authorized users. Organizations relying on this FTP server for file management, data backup, or content distribution may experience significant operational downtime and potential productivity losses during the period when the server is compromised.
Mitigation strategies for CVE-2009-3643 should focus on immediate software updates and implementation of defensive measures to prevent exploitation. The primary recommendation involves upgrading to a newer version of Dxmsoft XM Easy Personal FTP Server that contains patches addressing the input validation issues in the LIST and NLST commands. System administrators should also implement network-level protections such as firewall rules that limit FTP access to trusted IP addresses and monitor for unusual traffic patterns that might indicate exploitation attempts. Additionally, implementing input length restrictions and robust error handling within the FTP server configuration can provide additional defense-in-depth measures. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and organizations should consider implementing monitoring solutions that can detect and alert on abnormal FTP command usage patterns that might indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other network services and ensure comprehensive protection against similar attack vectors.