CVE-2009-3364 in FTPShell
Summary
by MITRE
Stack-based buffer overflow in FTPShell Client 4.1 RC2 allows remote FTP servers to execute arbitrary code via a long response to a PASV command.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/11/2024
The vulnerability identified as CVE-2009-3364 represents a critical stack-based buffer overflow flaw within the FTPShell Client version 4.1 RC2 software. This security weakness specifically manifests when the client processes responses from remote FTP servers during the passive mode connection establishment process. The vulnerability stems from inadequate input validation and bounds checking mechanisms within the client's handling of the PASV command response, which is a standard FTP protocol command used to establish data connections. When an attacker-controlled FTP server sends a maliciously crafted response containing excessive data in the PASV command reply, the client application fails to properly validate the response length before copying it into a fixed-size stack buffer. This fundamental flaw creates an exploitable condition where the overflow can overwrite adjacent stack memory, potentially allowing remote code execution with the privileges of the affected user.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with common attack methodologies documented in the MITRE ATT&CK framework under the T1059.007 technique for command and scripting interpreter. The attack vector specifically targets the network protocol handling component of the FTP client, leveraging the FTP protocol's inherent trust model where clients automatically accept responses from servers without sufficient validation. The vulnerability's classification as a stack-based buffer overflow places it within CWE-121, which describes buffer overflow conditions where data is written beyond the bounds of a stack-allocated buffer. This particular implementation flaw demonstrates poor memory management practices and highlights the importance of proper input sanitization and boundary checking in network protocol implementations. The impact extends beyond simple denial of service to full system compromise, as the attacker can potentially inject and execute malicious code within the context of the FTP client process.
The operational impact of this vulnerability is severe and far-reaching within enterprise environments that utilize FTPShell Client for file transfer operations. Organizations relying on this client for routine data exchanges become vulnerable to remote exploitation by malicious FTP servers, potentially leading to complete system compromise, data exfiltration, and lateral movement within network perimeters. The vulnerability affects not only individual user workstations but also enterprise file transfer infrastructure where the client might be used for automated processes or batch operations. Security analysts should consider this vulnerability as part of the broader attack surface when evaluating network security postures, particularly in environments where users might inadvertently connect to compromised or malicious FTP servers. The vulnerability's exploitation requires minimal prerequisites beyond the ability to control a remote FTP server, making it particularly dangerous in scenarios where users might encounter untrusted FTP services or where network traffic interception occurs.
Mitigation strategies for CVE-2009-3364 should prioritize immediate patching of the FTPShell Client application to version 4.1 RC3 or later, which contains the necessary fixes for the buffer overflow condition. Organizations should implement network segmentation and firewall rules to restrict FTP server access, particularly for users who do not require direct FTP connectivity. Network monitoring should be enhanced to detect unusual FTP protocol behavior, particularly unexpected long responses to PASV commands. Security teams should consider implementing network-based intrusion detection systems that can identify and block malicious FTP responses. Additionally, user education regarding the risks of connecting to untrusted FTP servers and the importance of verifying server authenticity should be emphasized. The vulnerability underscores the necessity of maintaining up-to-date software versions and implementing robust input validation mechanisms in all network protocol implementations. Organizations should also consider alternative file transfer protocols such as SFTP or FTPS that provide better security guarantees and are less susceptible to this class of vulnerability. Regular security assessments and penetration testing should include evaluation of network protocol handling components to identify similar buffer overflow conditions that could potentially be exploited in other applications.