CVE-2005-3812 in freeFTPd
Summary
by MITRE
freeFTPd 1.0.10 allows remote authenticated users to cause a denial of service (null dereference and crash) via a PORT command with missing arguments.
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Analysis
by VulDB Data Team • 06/12/2019
The vulnerability identified as CVE-2005-3812 affects freeFTPd version 1.0.10, a free FTP server implementation that was widely used in enterprise and educational environments during the mid-2000s. This particular flaw represents a critical security weakness that demonstrates poor input validation and error handling within the FTP protocol implementation. The vulnerability specifically targets the PORT command functionality, which is a standard FTP command used to establish data connections between FTP client and server. The issue occurs when an authenticated remote user sends a malformed PORT command with missing arguments, creating a condition that leads to a null pointer dereference in the server's processing logic. This type of vulnerability falls under the category of improper input validation as defined by CWE-20, which represents one of the most common software security flaws in the industry.
The technical exploitation of this vulnerability requires an attacker to first authenticate to the FTP server, which significantly reduces the attack surface compared to unauthenticated exploits. However, the impact remains severe as the flaw results in a complete system crash and denial of service condition. When the server processes the malformed PORT command, it attempts to access a null pointer reference in memory, causing the application to terminate abruptly and requiring manual restart of the FTP service. This behavior aligns with the ATT&CK technique T1499.004, which covers network denial of service attacks that target application availability. The null dereference condition creates an unpredictable crash state that can be reliably reproduced, making this vulnerability particularly dangerous in production environments where continuous availability is critical.
The operational impact of CVE-2005-3812 extends beyond simple service disruption, as it can be leveraged by malicious actors to create persistent availability issues that may affect business operations and user productivity. Organizations relying on freeFTPd for file transfer operations would experience complete service outages whenever an authenticated user or attacker sends the malformed command. The vulnerability's exploitation does not require advanced technical skills or specialized tools, making it accessible to a wide range of threat actors. From a security perspective, this flaw represents a classic example of how seemingly minor input validation issues can result in catastrophic system failures. The vulnerability also highlights the importance of proper error handling in network services, as the lack of defensive programming practices leads to uncontrolled application termination. Organizations using this version of freeFTPd should implement immediate mitigations including patching to newer versions, implementing network segmentation to limit access to the FTP service, or deploying intrusion detection systems to monitor for suspicious PORT command patterns.
The broader implications of this vulnerability extend to software development practices and security testing methodologies. It demonstrates the necessity of comprehensive input validation testing, particularly for network protocols that handle user-supplied data. The flaw's classification as a null pointer dereference aligns with CWE-476, which specifically addresses null pointer dereference conditions in software implementations. Modern security frameworks and compliance standards such as NIST SP 800-53 and ISO 27001 would consider this vulnerability as requiring immediate remediation due to its potential for service disruption and system instability. The vulnerability also serves as a historical example of why organizations should maintain up-to-date software versions and implement proper security monitoring practices to detect and respond to exploitation attempts. Given the age of the affected software and the availability of patches, the recommended mitigation strategy involves immediate upgrade to supported versions of freeFTPd or replacement with more modern and actively maintained FTP server solutions.