CVE-2008-2702 in ALFTP
Summary
by MITRE
Directory traversal vulnerability in the FTP client in ALTools ESTsoft ALFTP 4.1 beta 2 and 5.0 allows remote FTP servers to create or overwrite arbitrary files via a .. (dot dot) in a response to a LIST command, a related issue to CVE-2002-1345. NOTE: this can be leveraged for code execution by writing to a Startup folder.
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Analysis
by VulDB Data Team • 12/28/2024
The vulnerability described in CVE-2008-2702 represents a critical directory traversal flaw within the FTP client component of ALTools ESTsoft ALFTP version 4.1 beta 2 and 5.0. This weakness stems from inadequate input validation when processing directory listing responses from remote FTP servers, specifically during the handling of LIST command outputs. The vulnerability operates by exploiting the absence of proper sanitization for directory path components, allowing malicious FTP servers to manipulate file operations through the use of .. (dot dot) sequences in their responses. This issue is categorized under CWE-22 as a directory traversal vulnerability, which directly enables attackers to navigate outside of intended directories and manipulate the file system. The flaw is particularly concerning as it is related to CVE-2002-1345, indicating a pattern of similar vulnerabilities in FTP client implementations that have persisted across different versions and time periods.
The technical exploitation of this vulnerability occurs when an FTP client processes a malicious LIST command response containing directory traversal sequences. When the ALFTP client encounters these .. sequences in directory listings, it fails to properly validate or sanitize the path components, allowing the client to interpret these sequences as legitimate navigation commands. This misinterpretation enables the attacker-controlled FTP server to specify arbitrary file paths that the client will attempt to create or overwrite. The vulnerability is particularly dangerous because it can be leveraged for code execution through strategic file placement in system startup folders, where the operating system will automatically execute the malicious code upon system boot or user login. The attack vector requires the victim to connect to a malicious FTP server and execute a LIST command, which then triggers the vulnerable code path within the client application.
The operational impact of CVE-2008-2702 extends beyond simple file manipulation to encompass full system compromise through code execution capabilities. An attacker who successfully exploits this vulnerability can place malicious executables or scripts in the system's startup folders, ensuring persistent access and control over the compromised system. This persistence mechanism aligns with ATT&CK technique T1060 for persistence through registry run keys and T1547 for boot or logon initialization scripts. The vulnerability affects users who frequently connect to external FTP servers, particularly those in environments where trust is placed in remote servers without proper validation. The risk is exacerbated by the fact that the vulnerability is present in widely used FTP client software, making it a prime target for exploitation in various attack scenarios including phishing campaigns, malicious server compromises, and targeted attacks against specific user groups.
Mitigation strategies for this vulnerability should focus on both immediate protective measures and long-term architectural improvements. Users should avoid connecting to untrusted FTP servers and implement proper input validation within their FTP client configurations. The most effective immediate fix is to upgrade to a patched version of ALFTP that properly sanitizes directory path components in LIST command responses. Organizations should implement network segmentation to limit access to external FTP servers and deploy network monitoring solutions to detect suspicious FTP traffic patterns. From a security architecture perspective, the vulnerability highlights the importance of implementing proper path validation and sanitization in all file system operations, particularly those involving user-supplied or remote server-provided data. The fix should incorporate strict validation of path components to prevent directory traversal sequences from being processed as legitimate navigation commands, aligning with secure coding practices that prevent CWE-22 vulnerabilities through proper input validation and output encoding. Additionally, system administrators should regularly audit startup folders and implement application whitelisting to prevent unauthorized code execution, while also monitoring for unusual file creation patterns that might indicate exploitation attempts.