CVE-2007-6736 in pyftpdlib
Summary
by MITRE
Multiple directory traversal vulnerabilities in FTPServer.py in pyftpdlib before 0.2.0 allow remote authenticated users to access arbitrary files and directories via a .. (dot dot) in a (1) LIST, (2) STOR, or (3) RETR command.
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Analysis
by VulDB Data Team • 02/07/2019
The vulnerability described in CVE-2007-6736 represents a critical directory traversal flaw within the pyftpdlib FTP server implementation. This issue affects versions prior to 0.2.0 and specifically targets the FTPServer.py component that handles file operations through standard FTP commands. The vulnerability allows authenticated remote attackers to exploit the lack of proper input validation when processing directory navigation sequences, creating potential security risks that could lead to unauthorized data access and system compromise. The flaw manifests when users submit malicious paths containing dot-dot sequences that should be properly sanitized before file operations are executed.
The technical root cause of this vulnerability stems from inadequate path validation within the FTP server's command handling mechanism. When processing LIST, STOR, or RETR commands, the system fails to properly sanitize user-supplied paths that contain directory traversal sequences such as ../ or ..\, allowing attackers to navigate outside of intended directories and access arbitrary files on the system. This represents a classic path traversal vulnerability that violates fundamental security principles of input validation and access control. The vulnerability directly maps to 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 to encompass potential system compromise and data exfiltration. An authenticated attacker could leverage this vulnerability to access sensitive system files, configuration data, or user information that should remain protected. The vulnerability affects the core FTP functionality and could be exploited to escalate privileges or gain deeper system access, particularly when combined with other security weaknesses. This type of vulnerability provides attackers with a foothold that could enable further exploitation attempts against the system or network infrastructure.
Mitigation strategies for this vulnerability require immediate patching of the pyftpdlib library to version 0.2.0 or later where the directory traversal protections have been implemented. Organizations should also implement additional security measures including network segmentation, firewall rules to restrict FTP access, and monitoring of FTP traffic for suspicious path traversal attempts. The implementation of proper input validation and path sanitization should be enforced at multiple layers including application-level controls, network-level restrictions, and host-based security measures. Security teams should also consider implementing the principle of least privilege for FTP accounts and regularly audit FTP access logs for anomalous directory traversal patterns that could indicate exploitation attempts. This vulnerability aligns with ATT&CK technique T1078 which covers valid accounts and T1566 which covers credential harvesting, emphasizing the importance of proper access controls and monitoring.