CVE-2010-4790 in FilterFTP
Summary
by MITRE
Directory traversal vulnerability in FilterFTP 2.0.3, 2.0.5, and probably earlier versions, allows remote FTP servers to write arbitrary files via a "..\" (dot dot backslash) in a filename. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 02/09/2019
The directory traversal vulnerability identified as CVE-2010-4790 affects FilterFTP versions 2.0.3, 2.0.5, and potentially earlier releases, representing a critical security flaw that enables remote exploitation through improper input validation. This vulnerability specifically targets the filename handling mechanism within the FTP client software, creating a pathway for malicious actors to manipulate file operations and potentially execute arbitrary code or overwrite critical system files. The flaw manifests when the application processes filenames containing "..\" sequences, which should normally be rejected or properly sanitized to prevent directory traversal attacks.
The technical implementation of this vulnerability stems from inadequate validation of user-supplied data within the FTP client's file handling routines. When a remote FTP server provides a filename containing the "..\" sequence, the FilterFTP application fails to properly sanitize this input before processing it as a file path. This allows an attacker to escape the intended directory context and navigate to arbitrary locations within the file system. The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The flaw represents a classic example of insufficient input sanitization where the application does not properly validate or escape special characters that could alter the intended file path.
The operational impact of this vulnerability extends beyond simple file corruption or data loss, as it provides attackers with the capability to write arbitrary files to locations on the target system. This could enable privilege escalation, installation of malicious software, or complete system compromise depending on the execution context and permissions of the FilterFTP process. An attacker could leverage this vulnerability to overwrite system binaries, install backdoors, or modify configuration files that could persist across system reboots. The remote nature of the attack means that an unauthenticated attacker could exploit this vulnerability from outside the network perimeter, making it particularly dangerous for systems that expose FTP services to external networks.
Mitigation strategies for this vulnerability should include immediate patching of affected FilterFTP versions to address the directory traversal flaw through proper input validation and sanitization. Organizations should implement network segmentation to limit access to FTP services and deploy intrusion detection systems to monitor for suspicious filename patterns containing "..\" sequences. Additionally, the principle of least privilege should be enforced by running FilterFTP with minimal required permissions and ensuring that the application operates within restricted directory contexts. The vulnerability also highlights the importance of proper application security testing including input validation testing and security code reviews to identify similar flaws in other software components. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence mechanisms, as attackers could leverage the directory traversal capability to establish long-term access to compromised systems through file system manipulation and code injection.