CVE-2004-2488 in FTP Server
Summary
by MITRE
Directory traversal vulnerability in Nexgen FTP Server before 2.2.3.23 allows remote authenticated users to read or list arbitrary files via "C:" sequences in the (1) RETR (get), (2) NLST (ls), (3) LIST (ls), (4) RNFR, or (5) RNTO FTP commands.
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Analysis
by VulDB Data Team • 03/23/2025
The vulnerability described in CVE-2004-2488 represents a critical directory traversal flaw within the Nexgen FTP Server software, specifically affecting versions prior to 2.2.3.23. This security weakness enables authenticated remote attackers to bypass normal file access controls and gain unauthorized access to arbitrary files stored on the server filesystem. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied paths, allowing maliciously crafted file paths to traverse directory structures beyond the intended scope. The affected FTP commands include RETR for file retrieval, NLST and LIST for directory listing, as well as RNFR and RNTO for file renaming operations, creating multiple attack vectors for exploitation. This flaw fundamentally undermines the server's access control model by permitting attackers to navigate to sensitive system files, configuration data, or user information that should remain protected.
The technical implementation of this vulnerability exploits the server's failure to properly validate and sanitize file path inputs received through FTP commands. When an authenticated user submits a path containing "C:" sequences, the server processes these inputs without adequate sanitization, allowing the traversal logic to interpret the path components in unintended ways. This creates a condition where attackers can specify absolute paths or use relative path traversal techniques to access files outside of the designated FTP root directory. The vulnerability operates at the application layer and leverages the inherent trust model of FTP protocols, where authenticated sessions are assumed to have appropriate access rights. The flaw aligns with CWE-22, which categorizes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. These attacks exploit the fundamental principle that file systems should restrict access to resources based on proper authorization controls, but the vulnerability allows bypassing these protections through malformed input handling.
The operational impact of CVE-2004-2488 extends beyond simple unauthorized file access, potentially enabling attackers to extract sensitive information, compromise system integrity, and facilitate further attacks within the network infrastructure. An attacker who successfully exploits this vulnerability can potentially access system configuration files, user credentials, application source code, or other confidential data stored on the FTP server. The ability to list directories and retrieve files systematically allows for reconnaissance activities that could reveal network topology, application architecture, or other sensitive information. This vulnerability particularly affects environments where FTP servers host critical data or serve as entry points for broader network access, making it a significant concern for enterprise security. The impact is amplified because the vulnerability requires only authenticated access, meaning that attackers who have obtained legitimate FTP credentials can exploit this weakness without requiring additional privileges or complex attack vectors.
Security mitigations for this vulnerability should focus on immediate patching of the Nexgen FTP Server to version 2.2.3.23 or later, which contains the necessary fixes to properly validate and sanitize file path inputs. Organizations should implement robust input validation mechanisms that reject or sanitize any path components containing traversal sequences such as ".." or absolute path indicators. Network segmentation and firewall rules should be implemented to limit access to FTP services to only authorized users and systems. Additionally, implementing principle of least privilege access controls ensures that even if an attacker gains access to an FTP account, they cannot traverse to sensitive system areas. The vulnerability demonstrates the importance of proper secure coding practices and input validation, aligning with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting. Organizations should also consider implementing monitoring and logging for unusual FTP access patterns, particularly around file retrieval and directory listing operations that might indicate attempted exploitation of path traversal vulnerabilities. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other FTP server implementations and ensure comprehensive protection against directory traversal attacks.