CVE-2000-0644 in WFTPD
Summary
by MITRE
WFTPD and WFTPD Pro 2.41 allows remote attackers to cause a denial of service by executing a STAT command while the LIST command is still executing.
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Analysis
by VulDB Data Team • 03/19/2025
The vulnerability identified as CVE-2000-0644 affects WFTPD and WFTPD Pro version 2.41, representing a classic race condition scenario in network protocol implementations. This flaw manifests when a remote attacker can trigger a denial of service condition by sending a STAT command while a LIST command is actively processing, creating a timing dependency that leads to service disruption. The vulnerability resides in the FTP server's command handling mechanism where concurrent command execution is not properly synchronized, allowing malicious command interleaving that can cause the service to crash or become unresponsive.
The technical implementation of this vulnerability stems from inadequate thread management and command queue processing within the WFTPD software. When the LIST command begins execution, it typically holds system resources and locks certain internal data structures while enumerating directory contents. The STAT command, which normally retrieves server status information, when executed concurrently with LIST, creates a scenario where the server's internal state becomes inconsistent. This race condition occurs because the software does not properly implement mutual exclusion mechanisms to prevent concurrent access to shared resources during command processing. The flaw falls under CWE-362, which specifically addresses race conditions in concurrent programming, and demonstrates poor resource management practices in multi-threaded server applications.
From an operational impact perspective, this vulnerability presents a significant security risk to organizations relying on WFTPD servers for file transfer operations. The denial of service condition can persist for extended periods, potentially disrupting legitimate user access to file systems and causing business continuity issues. Attackers can exploit this vulnerability with minimal technical skill, requiring only basic FTP client tools to send the malicious command sequence. The impact extends beyond simple service disruption as it can be used as a precursor to more sophisticated attacks, potentially allowing attackers to gain insights into the system's operational state or as part of a broader reconnaissance effort. The vulnerability also demonstrates the importance of proper input validation and command sequencing in network services, as it highlights how seemingly innocuous command interactions can lead to critical system failures.
Mitigation strategies for this vulnerability should focus on implementing proper command synchronization mechanisms and enhancing the server's robustness against race conditions. Organizations should immediately apply vendor patches if available, as this vulnerability was likely addressed in subsequent releases. Network segmentation and access controls can help limit exposure by restricting which systems can connect to the affected FTP servers. Implementing intrusion detection systems that monitor for unusual command sequences may provide early warning of exploitation attempts. The remediation approach should align with ATT&CK technique T1499.004, which covers network denial of service, and emphasizes the need for proper application-level protections against race conditions. System administrators should also consider implementing command queuing mechanisms that ensure proper sequential execution of potentially conflicting commands, thereby preventing the scenario that leads to the vulnerability exploitation.