CVE-2008-6424 in FFFTP
Summary
by MITRE
Directory traversal vulnerability in FFFTP 1.96b allows remote FTP servers to create or overwrite arbitrary files via a response to an FTP LIST command with a filename that contains a .. (dot dot).
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Analysis
by VulDB Data Team • 10/31/2018
The vulnerability identified as CVE-2008-6424 represents a critical directory traversal flaw in FFFTP version 1.96b, a popular open-source ftp client for windows operating systems. This weakness stems from inadequate input validation within the client's handling of ftp list command responses, specifically when processing filenames that contain directory traversal sequences. The vulnerability enables malicious ftp servers to manipulate the client's file system operations through crafted responses that include .. (dot dot) sequences in filenames, effectively allowing attackers to write files to arbitrary locations on the victim's system.
From a technical perspective, the flaw manifests when FFFTP processes directory listings from ftp servers, failing to properly sanitize or validate filenames that contain directory traversal sequences. When an ftp server responds to a LIST command with a filename containing .. characters, the client interprets these sequences as navigation commands rather than literal filename characters. This misinterpretation occurs during the parsing of directory listing responses, where the client's path resolution logic does not adequately distinguish between legitimate directory navigation and malicious traversal attempts. The vulnerability specifically affects the client's handling of the LIST command response parsing, which is fundamental to displaying directory contents and managing file transfers.
The operational impact of this vulnerability is severe and far-reaching, as it enables remote code execution capabilities through file overwrites in arbitrary locations on the victim's system. Attackers can leverage this flaw to overwrite critical system files, install malicious software, or create backdoor access points by placing malicious files in directories such as system folders, user profile directories, or application data locations. The vulnerability essentially allows attackers to bypass normal file system access controls and potentially escalate privileges if they can target system-critical files. Additionally, the attack can be executed without any user interaction beyond establishing an ftp connection, making it particularly dangerous in automated exploitation scenarios.
This 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 also maps to several ATT&CK techniques including T1059 for command and scripting interpreter and T1078 for valid accounts, as attackers can use this vulnerability to establish persistent access through file overwrites. The vulnerability demonstrates a classic example of insufficient input validation in network protocol implementations, where client applications fail to properly validate server responses before executing file system operations. Organizations using FFFTP version 1.96b should immediately implement mitigations including updating to patched versions, implementing network segmentation, and monitoring for suspicious ftp server responses. The vulnerability highlights the importance of robust input validation in client applications that process untrusted network data and serves as a reminder of the critical security considerations in ftp client implementations.