CVE-2000-0648 in WFTPD
Summary
by MITRE
WFTPD and WFTPD Pro 2.41 allows local users to cause a denial of service by executing the RENAME TO (RNTO) command before a RENAME FROM (RNFR) command.
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Analysis
by VulDB Data Team • 03/15/2025
The vulnerability identified as CVE-2000-0648 affects WFTPD and WFTPD Pro version 2.41, representing a classic denial of service weakness in file transfer protocols. This flaw stems from improper handling of FTP command sequences, specifically the RENAME TO (RNTO) and RENAME FROM (RNFR) commands that are fundamental to file renaming operations within FTP servers. The vulnerability demonstrates a critical design flaw in the protocol implementation where the server fails to properly validate the sequence of rename commands before processing them.
The technical exploitation of this vulnerability occurs when a local user executes the RNTO command without first establishing the RNFR command, creating a state inconsistency within the FTP server's internal command processing logic. This improper command ordering triggers a condition where the server's file handling mechanisms become unstable, leading to system resource exhaustion or complete service termination. The flaw exists at the application layer of the network stack, specifically within the FTP protocol implementation where command validation and state management are insufficient to handle malformed command sequences.
From an operational perspective, this vulnerability presents a significant risk to system availability as local users can easily trigger a denial of service condition that affects the entire FTP service. The impact extends beyond simple service disruption since the vulnerability can potentially be exploited to cause system crashes or require manual intervention to restore normal operations. The local privilege requirement reduces the attack surface compared to remote exploits but still represents a serious security concern for systems where local access is possible or where privilege escalation might occur. This vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and demonstrates poor input validation practices in the FTP command processing subsystem.
The attack vector for CVE-2000-0648 operates through the standard FTP protocol interface, making it accessible to any user with local access to the system or those who can establish a local connection to the FTP service. The exploitation requires minimal technical expertise and can be accomplished through simple FTP client commands, making it particularly dangerous in environments where local access is not properly restricted. This vulnerability also connects to ATT&CK technique T1499.004, which covers network denial of service attacks, as the exploitation results in service unavailability that impacts system accessibility. The lack of proper state validation in the FTP server implementation creates a persistent weakness that can be repeatedly exploited until patched.
Mitigation strategies for this vulnerability should focus on implementing proper command sequence validation and state management within the FTP server software. System administrators should immediately upgrade to patched versions of WFTPD or WFTPD Pro that address this specific command ordering issue. Additionally, implementing proper access controls and limiting local access to FTP services can reduce the attack surface. Network segmentation and monitoring of FTP protocol activities can help detect anomalous command sequences that might indicate exploitation attempts. The vulnerability also underscores the importance of input validation and proper state management in protocol implementations, which should be addressed through comprehensive security testing and code review processes. Organizations should ensure that all FTP implementations include proper validation of command sequences and maintain consistent internal states to prevent similar issues from occurring in other protocol implementations.