CVE-2000-0133 in Tiny FTPdaemon
Summary
by MITRE
Buffer overflows in Tiny FTPd 0.52 beta3 FTP server allows users to execute commands via the STOR, RNTO, MKD, XMKD, RMD, XRMD, APPE, SIZE, and RNFR commands.
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Analysis
by VulDB Data Team • 10/19/2025
The vulnerability identified as CVE-2000-0133 represents a critical buffer overflow flaw within Tiny FTPd version 0.52 beta3, a lightweight file transfer protocol server implementation. This vulnerability manifests through multiple FTP commands including STOR for file storage, RNTO for renaming operations, MKD and XMKD for directory creation, RMD and XRMD for directory removal, APPE for appending data, SIZE for retrieving file sizes, and RNFR for renaming preparation. The flaw arises from insufficient input validation and boundary checking within the server's command processing routines, creating exploitable conditions where maliciously crafted input can overwrite adjacent memory regions.
The technical implementation of this vulnerability stems from the server's failure to properly validate the length of user-supplied data before copying it into fixed-size buffers. When users submit commands containing overly long arguments or malformed data sequences, the server's memory management routines become compromised, allowing attackers to overwrite return addresses, function pointers, or other critical control data structures. This memory corruption directly enables arbitrary code execution with the privileges of the FTP daemon process, typically running with elevated system permissions. The vulnerability affects the core FTP protocol implementation rather than specific network configurations, making it particularly dangerous as it can be exploited through standard FTP client connections without requiring special authentication.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with potential access to the underlying operating system and file system resources. Successful exploitation could result in complete system compromise, data exfiltration, or persistent backdoor installation. The vulnerability's exploitation is relatively straightforward since it targets common FTP operations that are frequently used in network administration and file transfer scenarios. Security researchers have classified this as a high-severity issue under CWE-121, which specifically addresses stack-based buffer overflow conditions, and it aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as attackers can leverage the vulnerability to execute arbitrary commands on compromised systems. The vulnerability's persistence across multiple FTP commands indicates a systemic flaw in the server's input handling architecture rather than isolated command-specific issues.
Mitigation strategies for CVE-2000-0133 require immediate patching of the Tiny FTPd server to a version that properly validates input lengths and implements proper buffer management techniques. Organizations should also implement network segmentation and access controls to limit exposure to the vulnerable FTP service, while monitoring for suspicious FTP activity that might indicate exploitation attempts. Additional defensive measures include deploying intrusion detection systems that can identify malformed FTP command sequences and implementing network-based firewalls that restrict FTP service access to trusted networks only. Security administrators should also consider migrating to more robust and actively maintained FTP server implementations such as vsftpd or ProFTPD, which have demonstrated better security track records and regular vulnerability updates. The vulnerability serves as a reminder of the critical importance of input validation and proper memory management in network services, particularly those handling user-supplied data in server environments.