CVE-2010-3101 in FTP Explorer
Summary
by MITRE
Directory traversal vulnerability in FTPx Corp FTP Explorer 10.5.19.1 for Windows, and probably earlier versions, allows remote FTP servers to write arbitrary files via a "..\" (dot dot backslash) in a filename.
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Analysis
by VulDB Data Team • 01/06/2018
The vulnerability identified as CVE-2010-3101 represents a critical directory traversal flaw affecting FTPx Corp FTP Explorer version 10.5.19.1 and potentially older releases. This security weakness resides in the client-side file handling mechanism of the FTP explorer application, which fails to properly validate filename inputs received from remote FTP servers. The vulnerability specifically manifests when the application processes filenames containing "..\" sequences, which are commonly used in directory traversal attacks to navigate outside of intended directories. This flaw enables malicious FTP servers to manipulate the local file system of vulnerable clients by writing files to arbitrary locations on the target system.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the FTP Explorer's file handling routines. When a remote FTP server sends a filename containing the "..\" sequence, the client application does not properly sanitize or validate this input before attempting to create or write files locally. This inadequate validation allows the application to interpret the traversal sequence as a legitimate path specification, thereby bypassing normal directory access controls. The vulnerability operates at the application layer and requires no special privileges or authentication to exploit, making it particularly dangerous in environments where users may connect to untrusted FTP servers. The flaw is classified as a path traversal vulnerability under CWE-22, which specifically addresses the issue of attackers manipulating file paths to access unauthorized resources.
The operational impact of this vulnerability extends beyond simple unauthorized file creation, as it provides attackers with the capability to overwrite existing system files, install malicious software, or modify critical application data. An attacker controlling a remote FTP server can leverage this vulnerability to write arbitrary files to any location on the victim's system where the FTP Explorer application has write permissions. This could result in privilege escalation, system compromise, or data corruption depending on the target locations and permissions. The vulnerability affects any user who connects to an attacker-controlled FTP server and executes the vulnerable FTP Explorer application, making it particularly concerning for organizations where users may connect to public or untrusted FTP services. The attack vector requires minimal user interaction beyond establishing a connection to the malicious server, as the exploitation occurs automatically during file transfer operations.
Mitigation strategies for this vulnerability should focus on both immediate remediation and long-term security improvements. The most effective immediate solution involves upgrading to a patched version of FTPx Corp FTP Explorer, as the vendor should have addressed the input validation issues in subsequent releases. Organizations should also implement network-level controls such as firewall rules that restrict access to FTP servers from untrusted networks, and consider deploying network segmentation to limit the potential impact of such attacks. Application-level mitigations include implementing strict filename validation that rejects any input containing directory traversal sequences, and running the FTP Explorer application with minimal required privileges to limit the damage potential. Additionally, users should be educated about the risks of connecting to untrusted FTP servers and the importance of verifying server authenticity before establishing connections. The vulnerability demonstrates the importance of proper input validation and the principle of least privilege in application security, aligning with security best practices outlined in the ATT&CK framework under the execution and privilege escalation tactics. Organizations should also consider implementing endpoint protection solutions that can detect and prevent unauthorized file system modifications, particularly in environments where legacy applications like FTP Explorer may be in use.