CVE-2017-16039 in hftp
Summary
by MITRE
`hftp` is a static http or ftp server `hftp` is vulnerable to a directory traversal issue, giving an attacker access to the filesystem by placing "../" in the url.
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Analysis
by VulDB Data Team • 02/14/2020
The CVE-2017-16039 vulnerability affects the hftp static http or ftp server implementation, representing a critical directory traversal flaw that exposes system files to unauthorized access. This vulnerability stems from inadequate input validation within the server's URL parsing mechanism, allowing malicious actors to navigate beyond the intended document root directory. The flaw specifically manifests when the server processes Uniform Resource Locators containing "../" sequences, which are commonly used to traverse parent directories in file systems. This type of vulnerability falls under the Common Weakness Enumeration category CWE-22, known as "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')", which is classified as a high-severity weakness in software security. The vulnerability exists because the hftp server does not properly sanitize or validate file paths before accessing them, creating an opportunity for attackers to bypass access controls and retrieve arbitrary files from the underlying file system. This weakness enables attackers to access sensitive data, configuration files, or system resources that should remain protected.
The operational impact of this vulnerability extends beyond simple file access, as it can lead to complete system compromise when combined with other attack vectors. An attacker exploiting this vulnerability can potentially access system configuration files, user credentials, application source code, or other sensitive information stored on the server. The directory traversal attack can be executed through simple URL manipulation, making it particularly dangerous as it requires minimal technical expertise to exploit. This vulnerability directly aligns with the MITRE ATT&CK framework's technique T1083, which covers "File and Directory Discovery", as attackers can systematically explore the file system to identify valuable targets. The attack surface is further expanded when the server is running with elevated privileges, as the traversal can potentially lead to privilege escalation or system-level compromise. The vulnerability affects not only the confidentiality of data but also the integrity and availability of the affected system, as attackers could potentially delete or modify critical files through the traversal mechanism.
Mitigation strategies for CVE-2017-16039 should focus on implementing proper input validation and path sanitization within the hftp server implementation. The most effective approach involves implementing a whitelist-based validation mechanism that only allows access to predetermined directories or file patterns, rather than relying on blacklisting or simple string filtering. Organizations should also implement proper access controls and authentication mechanisms to limit who can access the hftp server, as the directory traversal vulnerability alone may not provide complete system access without additional attack vectors. Network segmentation and firewall rules should be configured to restrict access to the hftp server to only authorized users or systems. Additionally, regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other services or applications. The implementation of secure coding practices, including the use of parameterized queries and proper path validation functions, should be enforced throughout the development lifecycle to prevent similar issues from occurring in future implementations. System administrators should also monitor access logs for suspicious directory traversal attempts and implement automated alerting mechanisms to detect potential exploitation attempts. The vulnerability highlights the importance of defense in depth strategies, where multiple layers of security controls work together to protect against various attack vectors including path traversal exploits.