CVE-2004-0330 in Serv-U FTP Server
Summary
by MITRE
Buffer overflow in Serv-U ftp before 5.0.0.4 allows remote authenticated users to execute arbitrary code via a long time zone argument to the MDTM command.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 07/13/2025
The vulnerability identified as CVE-2004-0330 represents a critical buffer overflow flaw within the Serv-U FTP server software version 5.0.0.3 and earlier. This issue specifically affects the handling of the MDTM command, which is used to retrieve the modification time of files on the server. The flaw arises from insufficient input validation when processing the time zone argument parameter, creating an exploitable condition that can be leveraged by authenticated remote attackers to gain arbitrary code execution privileges on the affected system. The vulnerability is particularly concerning as it requires only authentication to exploit, making it accessible to users who have legitimate access to the FTP service.
The technical implementation of this buffer overflow occurs when the Serv-U FTP server processes a malformed MDTM command containing an excessively long time zone argument. The software fails to properly validate the length of the input parameter before copying it into a fixed-size buffer, resulting in memory corruption that can be manipulated to overwrite adjacent memory locations. This memory corruption typically affects the return address on the stack, allowing an attacker to redirect execution flow to malicious code injected into the program's memory space. The vulnerability is classified as a classic stack-based buffer overflow, which is documented under CWE-121 in the Common Weakness Enumeration catalog and represents a fundamental software security flaw that has been consistently identified in network service implementations over many years.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete control over the affected FTP server. Once successfully exploited, an attacker can execute arbitrary commands with the privileges of the Serv-U service account, which typically runs with elevated system permissions. This access can be leveraged to establish persistent backdoors, exfiltrate sensitive data, modify server configurations, or use the compromised system as a launching point for further attacks within the network infrastructure. The vulnerability's remote execution capability means that attackers do not require physical access to the system, making it particularly dangerous for organizations that expose FTP services to external networks. The attack vector specifically targets the MDTM command which is part of the standard ftp protocol implementation and is commonly used by ftp clients for file synchronization and management operations.
Mitigation strategies for CVE-2004-0330 primarily focus on immediate software updates and network security controls. Organizations should immediately upgrade to Serv-U version 5.0.0.4 or later, which includes proper input validation for the MDTM command and addresses the buffer overflow condition. Network segmentation and access controls should be implemented to limit exposure of FTP services to trusted networks only, while disabling unnecessary FTP features and commands. Security monitoring should be enhanced to detect unusual MDTM command usage patterns that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1078 for valid accounts and T1059 for command and scripting interpreter, making it a significant concern for defensive security operations. Additionally, implementing proper input sanitization and bounds checking in application code can prevent similar vulnerabilities in other software components, aligning with security best practices recommended by organizations such as the SANS Institute and NIST. Regular security assessments and penetration testing should be conducted to identify and remediate similar buffer overflow vulnerabilities in legacy systems and network infrastructure components.