CVE-2002-0126 in BlackMoon FTP Server
Summary
by MITRE
Buffer overflow in BlackMoon FTP Server 1.0 through 1.5 allows remote attackers to execute arbitrary code via a long argument to (1) USER, (2) PASS, or (3) CWD.
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Analysis
by VulDB Data Team • 09/22/2025
The vulnerability identified as CVE-2002-0126 represents a critical buffer overflow flaw within the BlackMoon FTP Server versions 1.0 through 1.5. This security weakness resides in the server's handling of user authentication and directory change commands, specifically affecting the USER, PASS, and CWD commands that form the foundational elements of ftp protocol communication. The flaw stems from inadequate input validation mechanisms that fail to properly check the length of arguments provided during these critical ftp operations, creating an exploitable condition where maliciously crafted input can overwrite adjacent memory locations.
The technical implementation of this vulnerability follows a classic buffer overflow pattern where the ftp server's internal buffers cannot accommodate excessively long input strings. When an attacker sends a specially crafted argument exceeding the allocated buffer size to any of the three vulnerable commands, the excess data overflows into adjacent memory regions, potentially corrupting critical program execution structures. This overflow can overwrite return addresses, function pointers, or other control data within the server's memory space, providing an attacker with the opportunity to redirect program execution flow and ultimately execute arbitrary code on the target system. The vulnerability operates at the application layer and requires no authentication for exploitation, making it particularly dangerous as it can be triggered by any remote attacker with network access to the ftp service.
From an operational impact perspective, this vulnerability creates a severe security risk for organizations relying on BlackMoon FTP Server versions within the affected range. Successful exploitation allows remote attackers to gain complete control over the affected system, potentially enabling them to install malware, establish persistent backdoors, access sensitive data, or use the compromised server as a launching point for further attacks against the internal network. The vulnerability's accessibility through standard ftp protocol connections means that any system running an affected version of BlackMoon FTP Server is immediately at risk, regardless of network segmentation or firewall configurations. Additionally, the lack of authentication requirements for exploitation means that even basic network scanning can identify vulnerable systems without requiring additional reconnaissance or credential acquisition efforts.
The mitigation strategies for this vulnerability primarily focus on immediate remediation through software updates and patches provided by the vendor. Organizations should prioritize upgrading to BlackMoon FTP Server versions that have addressed this buffer overflow issue, as no official patches were available for the affected versions at the time of this vulnerability disclosure. Network administrators should also implement additional protective measures including firewall rules that restrict ftp service access to trusted networks, monitoring for suspicious ftp traffic patterns, and implementing intrusion detection systems that can identify exploitation attempts. The vulnerability aligns with CWE-121, which categorizes buffer overflow conditions as a fundamental weakness in software design that can lead to arbitrary code execution. From an ATT&CK framework perspective, this vulnerability maps to techniques involving remote code execution through software exploitation and can be classified under the T1190 category for exploits for client execution, potentially enabling adversaries to establish persistent access and move laterally within compromised networks.