CVE-2005-2126 in Internet Explorer
Summary
by MITRE
The FTP client in Windows XP SP1 and Server 2003, and Internet Explorer 6 SP1 on Windows 2000 SP4, when "Enable Folder View for FTP Sites" is enabled and the user manually initiates a file transfer, allows user-assisted, remote FTP servers to overwrite files in arbitrary locations via crafted filenames.
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Analysis
by VulDB Data Team • 06/30/2025
The vulnerability described in CVE-2005-2126 represents a critical file system manipulation flaw affecting Microsoft Windows operating systems and Internet Explorer versions. This issue specifically targets the File Transfer Protocol client implementation within these systems, creating a path for remote attackers to execute unauthorized file operations through carefully crafted filenames. The vulnerability manifests when users manually initiate file transfers to FTP servers while the "Enable Folder View for FTP Sites" configuration is active, establishing a scenario where malicious servers can manipulate the local file system through seemingly benign file transfer operations.
The technical root cause of this vulnerability lies in inadequate input validation and path resolution mechanisms within the FTP client implementation. When users interact with FTP sites that have folder view enabled, the client processes filenames received from remote servers without sufficient sanitization of special characters or path traversal sequences. This flaw enables attackers to construct filenames that contain directory traversal components such as "../" sequences or other malicious path constructs that can navigate beyond the intended target directories. The vulnerability operates under the Common Weakness Enumeration classification of CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as it allows attackers to overwrite files in arbitrary system locations with elevated privileges. This capability enables attackers to modify critical system files, replace executables, or manipulate configuration data that could lead to complete system compromise. The vulnerability is particularly dangerous because it requires only user interaction to initiate the malicious file transfer, making it exploitable through social engineering or phishing attacks where users might be tricked into connecting to malicious FTP servers. The attack vector specifically targets the user-assisted execution model, meaning that while the vulnerability requires user action, the actual exploitation can occur entirely through remote server manipulation without requiring local system compromise.
The affected systems include Windows XP Service Pack 1, Windows Server 2003, and Internet Explorer 6 Service Pack 4 on Windows 2000 SP4, representing a significant portion of Microsoft's user base at the time of vulnerability disclosure. This vulnerability directly maps to several tactics in the MITRE ATT&CK framework, particularly focusing on privilege escalation through file system manipulation and execution of malicious code through user interaction. The attack chain typically involves initial user engagement with a malicious FTP server followed by automatic file system modification based on crafted filenames, potentially leading to persistent backdoor installation or system corruption.
Mitigation strategies for this vulnerability include disabling the "Enable Folder View for FTP Sites" option in Internet Explorer settings, which removes the attack surface by preventing the problematic file system interaction patterns. Microsoft released patches for affected systems, and system administrators should ensure all systems are updated with the appropriate security updates. Additional protective measures include implementing network-level controls to restrict FTP access, using firewall rules to limit outbound FTP connections, and educating users about the risks of connecting to untrusted FTP servers. The vulnerability highlights the importance of input validation and proper path resolution in client-side applications, emphasizing that even seemingly benign features like folder view can create security risks when not properly secured against malicious input manipulation.