CVE-2004-1642 in WFTPD Pro Server
Summary
by MITRE
WFTPD Pro Server 3.21 allows remote authenticated users to cause a denial of service (crash) via a series of long MLIST commands.
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Analysis
by VulDB Data Team • 07/06/2025
The vulnerability identified as CVE-2004-1642 affects WFTPD Pro Server version 3.21, a widely used file transfer protocol server implementation that was prevalent in enterprise environments during the early 2000s. This security flaw represents a classic denial of service vulnerability that specifically targets the server's handling of MLIST commands within the FTP protocol framework. The vulnerability is particularly concerning because it requires only authenticated access to exploit, meaning that an attacker who has already gained valid credentials can trigger a system crash that renders the file transfer service completely unavailable to legitimate users. The MLIST command, which is used to retrieve directory listings in a machine-readable format, becomes a vector for service disruption when processed in excessive quantities or with overly long parameter sequences. This type of vulnerability falls under the category of improper input validation and resource exhaustion, where the server fails to properly handle malformed or excessively long command sequences that could consume system resources or trigger memory corruption issues.
The technical exploitation of this vulnerability involves sending a series of MLIST commands that are progressively longer in nature, causing the WFTPD Pro Server to allocate excessive memory resources or encounter buffer overflow conditions during command processing. The server's implementation lacks proper bounds checking and input sanitization mechanisms that would normally prevent such sequences from overwhelming the system's memory management capabilities. When these long MLIST commands are processed in rapid succession, they can cause the server process to crash or become unresponsive, effectively terminating the FTP service and preventing legitimate users from accessing files through the affected server. This vulnerability demonstrates a fundamental weakness in the server's command parsing logic and resource management, where the system does not adequately protect against malicious or malformed command sequences that could be used to exhaust available resources or trigger unexpected behavior in the application's memory handling routines.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader implications for enterprise security and business continuity. Organizations relying on WFTPD Pro Server 3.21 for file transfer operations face significant risk of operational downtime that could affect critical business processes, data exchange operations, and user productivity. The authenticated nature of the exploit means that this vulnerability could be leveraged by insider threats or compromised accounts, making it particularly dangerous for environments where access controls may not be sufficiently strict. The vulnerability also highlights the importance of proper input validation and resource management in server applications, as it demonstrates how seemingly benign FTP commands can be weaponized to cause system instability. From a cybersecurity perspective, this vulnerability represents a classic example of how protocol implementation flaws can be exploited to achieve denial of service outcomes, potentially serving as a stepping stone for more sophisticated attacks that might follow such service disruption events. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and could be categorized under ATT&CK technique T1499.004 for endpoint denial of service, where the attacker targets specific endpoints to disrupt service availability.
Mitigation strategies for CVE-2004-1642 should focus on immediate patching of the WFTPD Pro Server software to the latest available version that contains fixes for the MLIST command handling logic. Organizations should implement network-level controls to monitor and restrict FTP command sequences that exceed normal parameters, particularly those involving MLIST operations. Access controls should be reviewed and strengthened to limit the number of authenticated users who can access the FTP server, reducing the attack surface for this particular vulnerability. System administrators should also implement monitoring solutions that can detect unusual command patterns or excessive resource consumption that might indicate attempted exploitation of this vulnerability. Additionally, network segmentation should be employed to isolate FTP services from critical business systems, minimizing the potential impact of a successful exploitation event. The remediation approach should also include comprehensive testing of the patched software to ensure that legitimate FTP operations continue to function correctly while the vulnerability is addressed. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious FTP command sequences that match the characteristics of this known vulnerability pattern.