CVE-2002-0826 in WS_FTP Server
Summary
by MITRE
Buffer overflow in WS_FTP FTP Server 3.1.1 allows remote authenticated users to execute arbitrary code via a long SITE CPWD command.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/13/2025
The vulnerability identified as CVE-2002-0826 represents a critical buffer overflow flaw in WS_FTP Server version 3.1.1 that specifically affects the SITE CPWD command functionality. This issue arises from insufficient input validation within the server's command processing mechanism, creating a condition where maliciously crafted input can overwrite adjacent memory locations. The vulnerability is particularly dangerous because it requires only authenticated access, meaning that an attacker who has already established a valid user session can exploit this flaw to gain complete control over the affected system. The buffer overflow occurs when the server processes the SITE CPWD command with excessively long input parameters, causing the program to write data beyond the allocated buffer boundaries and potentially overwrite critical program execution data.
From a technical perspective, this vulnerability maps directly to CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The flaw operates through a classic stack-based buffer overflow scenario where the server's command handling routine fails to properly validate the length of input data before copying it into fixed-size buffers. The authenticated nature of this exploit means that attackers do not need to perform additional reconnaissance or credential harvesting, as they can leverage existing valid user sessions to deliver malicious payloads. This characteristic significantly reduces the attack surface complexity and increases the likelihood of successful exploitation.
The operational impact of CVE-2002-0826 extends far beyond simple privilege escalation, as successful exploitation can lead to complete system compromise and unauthorized access to sensitive data. Attackers who successfully exploit this vulnerability can execute arbitrary code with the privileges of the WS_FTP Server process, which typically runs with elevated system permissions. This scenario creates a persistent threat vector that can be leveraged for data exfiltration, system reconnaissance, and establishment of backdoors. The vulnerability also poses significant risk to network infrastructure, as compromised FTP servers can serve as launching points for further attacks against internal network resources. Organizations relying on WS_FTP Server 3.1.1 face potential exposure to advanced persistent threats that can remain undetected for extended periods.
Mitigation strategies for this vulnerability should prioritize immediate patching of the affected WS_FTP Server version, as the vendor has released updates to address this specific buffer overflow condition. Network segmentation and access controls should be implemented to limit the potential impact of successful exploitation by restricting access to the affected FTP server. Additionally, monitoring for suspicious SITE CPWD command usage and implementing intrusion detection systems can help identify potential exploitation attempts. The remediation approach should also include comprehensive vulnerability assessments to identify other potentially affected systems running older versions of WS_FTP Server or similar FTP implementations. Security teams should consider implementing application whitelisting policies to prevent unauthorized execution of potentially malicious code and establish robust incident response procedures to address potential exploitation attempts. This vulnerability also highlights the importance of regular security updates and the need for organizations to maintain current knowledge of known vulnerabilities affecting their deployed software systems, as outlined in the ATT&CK framework's mitigation strategies for privilege escalation and code execution techniques.