CVE-2017-16164 in desafio
Summary
by MITRE
desafio is a simple web server. desafio is vulnerable to a directory traversal issue, giving an attacker access to the filesystem by placing "../" in the url, but is limited to accessing only .html files.
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Analysis
by VulDB Data Team • 02/16/2020
The vulnerability identified as CVE-2017-16164 affects desafio, a simple web server implementation that suffers from a directory traversal flaw. This represents a critical security weakness that allows unauthorized access to the underlying file system through carefully crafted url parameters. The vulnerability specifically manifests when an attacker includes "../" sequences in the url path, enabling them to navigate beyond the intended web root directory and access files on the server. This type of vulnerability falls under the category of path traversal attacks and is classified as CWE-22 according to the Common Weakness Enumeration framework, which specifically addresses improper limitation of a pathname to a restricted directory.
The technical implementation of this vulnerability stems from inadequate input validation and sanitization within the web server's file access mechanisms. When desafio processes incoming requests, it fails to properly validate or sanitize the url parameters that contain file paths, allowing malicious users to manipulate the path traversal sequences. The limitation to accessing only .html files suggests that the web server may have implemented some form of file extension filtering or content type restrictions, but this does not prevent the fundamental directory traversal attack. Attackers can still leverage this vulnerability to access sensitive configuration files, source code, or other valuable data that might be stored in the server's file system, even if they are not directly accessible through the web interface.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with a foothold for further exploitation within the system. While the restriction to .html files limits the scope of what can be directly read, it does not prevent attackers from accessing other sensitive files that may contain credentials, configuration information, or application logic that could be used for privilege escalation or additional attacks. The vulnerability creates a potential attack vector for attackers to gather intelligence about the server environment, application structure, and potentially identify other vulnerabilities that could be exploited. This aligns with ATT&CK technique T1083 (File and Directory Discovery) which describes how adversaries attempt to gather information about files and directories on compromised systems.
The mitigation strategies for this vulnerability require a comprehensive approach to input validation and access control. The most effective solution involves implementing proper input sanitization that filters out or rejects path traversal sequences such as "../" and "..\" patterns before they are processed by the file system. Additionally, the web server should implement strict directory access controls that ensure all file access operations are confined to a predetermined web root directory, regardless of user input. This can be achieved through proper path resolution techniques that normalize file paths and prevent directory traversal attempts. The implementation of a whitelist approach for allowed file extensions and access patterns would further enhance security. Organizations should also consider implementing proper logging and monitoring of file access attempts to detect potential exploitation attempts. The vulnerability demonstrates the importance of following secure coding practices and input validation as outlined in OWASP Top Ten security principles, specifically addressing the risk of path traversal attacks that can compromise the entire file system accessibility of web applications.