CVE-2004-0255 in FTP Server
Summary
by MITRE
Xlight 1.52, with log to screen enabled, allows remote attackers to cause a denial of service by requesting a long directory consisting of . (dot) and / (slash) characters, which causes the server to crash when the administrator views the log file, possibly triggering a buffer overflow.
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Analysis
by VulDB Data Team • 08/17/2025
The vulnerability identified as CVE-2004-0255 affects Xlight FTP server version 1.52 and represents a classic denial of service flaw that exploits improper input validation in log file handling. This issue demonstrates a fundamental security weakness in how the software processes and displays directory paths in its logging mechanism, creating an exploitable condition that can be triggered remotely by malicious actors.
The technical flaw manifests when an attacker constructs a specially crafted directory path consisting of numerous dot and slash characters, effectively creating an excessively long path string. When the FTP server processes this malformed input and logs it to the screen, the system encounters a buffer overflow condition during log file viewing operations. This buffer overflow occurs because the application fails to properly validate the length of directory paths before attempting to display them, leading to memory corruption that ultimately causes the server to crash and become unavailable to legitimate users.
From an operational perspective, this vulnerability presents a significant risk to system availability and service integrity. The attack requires minimal technical expertise to execute, making it particularly dangerous as it can be exploited by attackers with basic networking knowledge. The remote nature of the attack means that administrators cannot easily prevent or detect the exploit before it occurs, as the malicious input can be sent over the network without requiring authentication or direct system access. The impact extends beyond simple service disruption to potentially compromising the entire FTP service availability, which could affect critical business operations that depend on file transfer capabilities.
The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and demonstrates how improper input validation can lead to memory corruption issues. From the MITRE ATT&CK framework perspective, this represents a denial of service attack technique that falls under the category of service disruption, potentially serving as a precursor to more sophisticated attacks that might exploit the same underlying vulnerability for privilege escalation or information disclosure. Organizations should implement immediate mitigations including disabling log to screen functionality, implementing proper input validation for directory paths, and applying the vendor-provided patch to address this specific buffer overflow condition.
The root cause of this vulnerability stems from inadequate bounds checking and input sanitization within the logging subsystem of Xlight FTP server. When directory paths are processed for logging, the application does not enforce reasonable limits on path length or properly sanitize special characters, creating an environment where maliciously constructed input can trigger memory corruption. This flaw highlights the importance of defensive programming practices and the necessity of implementing proper input validation at all levels of application processing, particularly in components that handle user-provided data and display it to administrators. The vulnerability serves as a reminder that even seemingly benign features like logging can become attack vectors when proper security measures are not implemented.