CVE-2003-0766 in FTP Desktop Client
Summary
by MITRE
Multiple heap-based buffer overflows in FTP Desktop client 3.5, and possibly earlier versions, allow remote malicious servers to execute arbitrary code via (1) a long FTP banner, (2) a long response to a USER copmmand, or (3) a long response to a PASS command.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/27/2025
The vulnerability described in CVE-2003-0766 represents a critical heap-based buffer overflow in FTP Desktop client version 3.5 and potentially earlier releases. This flaw resides in the client's handling of responses from FTP servers, specifically during the initial connection phase when establishing communication with remote servers. The vulnerability manifests when the client processes untrusted input from malicious FTP servers without proper bounds checking, creating opportunities for attackers to exploit memory corruption vulnerabilities. The affected parameters include the FTP banner response, user authentication responses, and password authentication responses, all of which are fundamental components of the standard ftp protocol negotiation process. This vulnerability operates at the application layer and can be exploited through network-based attacks without requiring any local privileges or user interaction beyond connecting to a malicious server.
The technical implementation of this vulnerability follows a classic heap overflow pattern where insufficient input validation allows attackers to write data beyond the allocated buffer boundaries in the client's memory space. When processing a long FTP banner response, the client's string handling functions fail to validate the length of incoming data, causing data to overwrite adjacent memory locations in the heap. Similarly, the USER and PASS command responses are processed without proper boundary checks, allowing attackers to craft malicious responses that trigger buffer overflows. These buffer overflows can lead to arbitrary code execution with the privileges of the user running the FTP client, effectively providing attackers with complete control over the affected system. The vulnerability demonstrates characteristics consistent with CWE-121 heap-based buffer overflow, which is classified as a memory safety error that allows attackers to overwrite memory and potentially execute malicious code.
The operational impact of this vulnerability is severe as it enables remote code execution against vulnerable systems with minimal attack prerequisites. An attacker only needs to set up a malicious FTP server and convince a victim to connect to it, making this vector particularly dangerous in environments where users frequently connect to external FTP servers. The attack can result in complete system compromise, data theft, privilege escalation, and potential lateral movement within networks. This vulnerability affects the fundamental security posture of any system using the affected FTP client, as it can be exploited regardless of network segmentation or firewall configurations. The exploitation can occur without requiring authentication or specialized attack tools beyond basic server setup, making it a high-risk vulnerability that could be leveraged for widespread compromise across organizations. The vulnerability also aligns with ATT&CK technique T1190 which involves exploiting vulnerabilities in remote services to gain initial access to systems.
Mitigation strategies for CVE-2003-0766 should focus on immediate patching of the affected FTP client software, as version 3.5 and earlier releases are vulnerable to this attack vector. Organizations should implement network segmentation to limit access to external FTP servers and consider using more secure protocols such as SFTP or FTPS for file transfers. Additionally, implementing network-based intrusion detection systems can help detect anomalous FTP traffic patterns that may indicate exploitation attempts. The vulnerability can be addressed through input validation and bounds checking implementations that ensure all FTP responses are properly sanitized before processing. System administrators should also consider disabling FTP client functionality if not essential for business operations, and implement regular security assessments to identify and remediate similar vulnerabilities in other network client applications. Organizations should maintain updated vulnerability management processes that include regular patching of client applications and monitoring for exploitation attempts against known vulnerabilities.