CVE-2004-2769 in FTP Server
Summary
by MITRE
Cerberus FTP Server before 4.0.3.0 allows remote authenticated users to list hidden files, even when the "Display hidden files" option is enabled, via the (1) MLSD or (2) MLST commands.
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Analysis
by VulDB Data Team • 07/05/2025
The vulnerability identified as CVE-2004-2769 affects Cerberus FTP Server versions prior to 4.0.3.0 and represents a significant security flaw in file access controls that undermines the confidentiality and integrity of file systems. This issue specifically targets the server's handling of hidden files and demonstrates a failure in proper access control implementation that allows authenticated users to bypass intended restrictions. The vulnerability operates through the use of two specific FTP commands: MLSD (Machine List Directory) and MLST (Machine List File), which are part of the FTP protocol extensions defined in RFC 3659 for machine-readable directory listings. These commands are designed to provide structured information about files and directories, but in the affected versions of Cerberus FTP Server, they fail to properly respect the configured "Display hidden files" option.
The technical nature of this flaw stems from improper validation and filtering of file listing requests within the server's command processing logic. When authenticated users issue MLSD or MLST commands, the server should respect the configured settings that determine whether hidden files should be visible to users. However, the vulnerability allows these commands to return information about hidden files regardless of the display settings, effectively providing unauthorized access to file system metadata that should remain concealed. This represents a clear violation of the principle of least privilege and demonstrates inadequate input validation and access control enforcement within the server's core functionality. The flaw is classified under CWE-284 (Improper Access Control) which specifically addresses situations where system components fail to properly enforce access restrictions.
Operationally, this vulnerability creates serious security implications for organizations relying on Cerberus FTP Server for file transfer operations. Remote authenticated users who have legitimate access to the FTP server can exploit this weakness to discover sensitive files that are typically hidden from normal directory listings. This could include system configuration files, log files, backup data, or other sensitive information that administrators intentionally hide from regular users. The impact extends beyond simple information disclosure as it can enable further exploitation attempts by revealing the existence of potentially vulnerable files or system components that might not be visible through normal directory traversal. Attackers could use this information to craft more targeted attacks against specific files or to map the overall structure of the file system in greater detail than intended.
The exploitation of this vulnerability requires only authenticated access to the FTP server, making it particularly concerning as it can be leveraged by insiders or compromised legitimate users. The MLSD and MLST commands are commonly used by FTP clients and automated systems for directory enumeration, making this vulnerability particularly dangerous in environments where automated processes interact with the FTP server. Organizations implementing this server should consider the broader implications of this vulnerability within their security posture, as it can facilitate reconnaissance activities that would otherwise be blocked by proper access controls. The flaw also demonstrates a lack of proper security testing and validation of core FTP functionality, particularly in how the server handles file system metadata access requests.
Mitigation strategies for CVE-2004-2769 primarily involve upgrading to Cerberus FTP Server version 4.0.3.0 or later, which contains the necessary patches to address the access control bypass. System administrators should also implement additional monitoring and logging of FTP commands, particularly MLSD and MLST operations, to detect potential exploitation attempts. Network segmentation and access control measures should be reinforced to limit the impact of any successful exploitation, and regular security assessments should be conducted to identify similar vulnerabilities in other network services. The vulnerability aligns with ATT&CK technique T1083 (File and Directory Discovery) which describes methods used to gather information about file systems and directories. Organizations should also consider implementing automated vulnerability scanning tools that can detect the presence of this specific vulnerability in their environments. Proper configuration management and regular patch management processes are essential to prevent similar issues from arising in other FTP server implementations or related network services.