CVE-2008-4247 in NetBSD
Summary
by MITRE
ftpd in OpenBSD 4.3, FreeBSD 7.0, NetBSD 4.0, Solaris, and possibly other operating systems interprets long commands from an FTP client as multiple commands, which allows remote attackers to conduct cross-site request forgery (CSRF) attacks and execute arbitrary FTP commands via a long ftp:// URI that leverages an existing session from the FTP client implementation in a web browser.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/27/2025
The vulnerability described in CVE-2008-4247 represents a critical security flaw in various Unix-like operating systems' FTP server implementations, specifically affecting ftpd services running on OpenBSD 4.3, FreeBSD 7.0, NetBSD 4.0, and Solaris systems. This vulnerability stems from improper handling of command parsing within the FTP protocol implementation, where the server fails to properly validate command length limits. The flaw creates a dangerous condition where a single long command can be interpreted as multiple discrete commands by the FTP daemon, leading to unexpected behavior that can be exploited by remote attackers. The issue is particularly concerning because it affects multiple operating systems simultaneously, indicating a widespread implementation flaw in the underlying FTP protocol handling mechanisms.
The technical exploitation of this vulnerability occurs through the manipulation of ftp:// URIs within web browsers, leveraging the inherent trust relationships between web browsers and FTP client implementations. When a web browser encounters a long ftp:// URI, the FTP client within the browser attempts to process the malformed command sequence, causing the ftpd service to interpret the extended input as multiple separate commands. This behavior creates a cross-site request forgery scenario where an attacker can craft malicious URLs that, when visited by a user, trigger unintended FTP operations within the context of an existing FTP session. The vulnerability essentially allows attackers to bypass normal command validation procedures and execute arbitrary FTP commands without proper authentication, as the commands are processed within the context of an already established session.
The operational impact of this vulnerability extends beyond simple command execution, as it creates a potential vector for complete system compromise when combined with existing session information. Attackers can leverage this flaw to perform unauthorized file operations, directory traversal, and potentially gain access to sensitive system resources. The vulnerability is particularly dangerous in environments where users frequently browse the web and interact with FTP services, as the attack can be executed simply by visiting a malicious website. The cross-site request forgery aspect means that victims do not need to actively engage with the malicious content, as the exploitation occurs automatically when the browser processes the crafted URI. This makes the vulnerability particularly effective for automated attacks and increases the potential for widespread exploitation across multiple systems.
Mitigation strategies for CVE-2008-4247 require immediate system updates and configuration hardening to address the fundamental command parsing flaw. System administrators should prioritize patching affected operating systems to the latest stable releases that contain fixes for the command length validation issue. Additionally, implementing network-level restrictions such as firewall rules that limit FTP service access to trusted networks can help reduce exposure. The vulnerability aligns with CWE-129, which describes improper validation of length of input buffers, and demonstrates characteristics consistent with ATT&CK technique T1071.004 for application layer protocol tunneling. Organizations should also consider implementing web application firewalls to monitor and filter potentially malicious ftp:// URI patterns, and establish strict access controls for FTP services to prevent unauthorized command execution. Regular security audits of FTP configurations and monitoring for unusual command sequences can help detect exploitation attempts and maintain system integrity.