CVE-2008-4136 in Personal FTP Server
Summary
by MITRE
Michael Roth Software Personal FTP Server (PFT) 6.0f allows remote attackers to cause a denial of service (service crash) via multiple RETR commands, possibly involving long filenames.
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Analysis
by VulDB Data Team • 11/04/2024
The CVE-2008-4136 vulnerability affects Michael Roth Software Personal FTP Server version 6.0f, representing a significant denial of service weakness that can be exploited remotely by attackers. This vulnerability specifically targets the RETR command functionality within the FTP server implementation, where multiple consecutive RETR requests can trigger a service crash. The flaw demonstrates characteristics consistent with improper input validation and resource handling issues that are commonly classified under CWE-129 Input Validation and CWE-400 Uncontrolled Resource Consumption. The vulnerability exists in the server's handling of file retrieval operations, where the system fails to properly manage repeated requests for file transfers, particularly when dealing with extended filename lengths that may exceed expected buffer limits or processing capabilities.
The technical exploitation of this vulnerability involves sending multiple RETR commands to the affected FTP server, which causes the service to become unresponsive or crash entirely. This type of attack falls under the ATT&CK technique T1499.004 for Network Denial of Service, where adversaries leverage service-specific weaknesses to disrupt availability. The combination of multiple RETR commands with potentially long filenames creates a scenario where the server's internal state management becomes corrupted or overwhelmed, leading to the termination of the FTP service. The vulnerability is particularly concerning because it requires minimal privileges to exploit and can be executed remotely, making it accessible to any attacker with network access to the affected server.
The operational impact of this vulnerability extends beyond simple service disruption, as it can result in complete unavailability of the FTP service for legitimate users while also potentially exposing the system to further exploitation attempts. When the service crashes, it may leave the server in an inconsistent state that could be leveraged for additional attacks or require manual intervention to restore normal operations. Organizations relying on Personal FTP Server for file transfers, backups, or data sharing may experience significant downtime and potential data access issues. The vulnerability also highlights the importance of proper error handling and resource management in server applications, as the failure to implement adequate safeguards against repeated command processing can lead to complete service outages.
Mitigation strategies for this vulnerability should focus on immediate patching of the affected software version, as well as implementing network-level controls to limit the number of concurrent RETR commands that can be processed. System administrators should consider implementing rate limiting mechanisms and connection throttling to prevent abuse of the FTP server functionality. The solution involves updating to a patched version of Personal FTP Server that properly handles multiple RETR commands and implements appropriate buffer management for long filenames. Additionally, monitoring systems should be deployed to detect unusual patterns of RETR command execution that could indicate an attempted exploitation, as outlined in the ATT&CK framework for defensive measures. Organizations should also consider implementing redundant FTP services or alternative file transfer protocols to minimize the impact of such service disruptions on their operations.