CVE-2017-16152 in static-html-server
Summary
by MITRE
static-html-server is a static file server. static-html-server 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 • 02/16/2020
The vulnerability identified as CVE-2017-16152 affects static-html-server, a lightweight static file server implementation that serves web content directly from the file system. This particular vulnerability represents a classic directory traversal attack vector that allows malicious actors to access files and directories beyond the intended serving scope. The flaw manifests when the application fails to properly sanitize user-supplied input in URL paths, enabling attackers to manipulate file access through crafted path sequences. The vulnerability specifically occurs when the server processes URLs containing ../ sequences, which are standard Unix-style relative path references that navigate up one directory level in the file system hierarchy.
This directory traversal vulnerability stems from inadequate input validation and path sanitization within the static-html-server application. When a user submits a URL containing ../ sequences, the server processes these references without proper restrictions, allowing the attacker to traverse the file system and access sensitive files that should remain protected. The technical implementation flaw lies in the server's failure to canonicalize or normalize file paths before serving content, creating a direct pathway to arbitrary file access. This type of vulnerability is categorized under CWE-22, which specifically addresses Improper Limitation of a Pathname to a Restricted Directory, commonly known as Path Traversal or Directory Traversal. The vulnerability enables attackers to potentially access system files, configuration files, source code, and other sensitive data that may be stored on the server.
The operational impact of this vulnerability is significant as it provides attackers with unauthorized access to the underlying file system, potentially exposing sensitive information, credentials, or system configuration details. An attacker could leverage this vulnerability to access not only the web root directory but potentially gain access to system directories, user files, and application configuration data. The attack surface is particularly concerning for servers hosting web applications, as directory traversal vulnerabilities often provide the initial foothold for more sophisticated attacks. This vulnerability aligns with ATT&CK technique T1083, which covers File and Directory Discovery, as attackers can systematically enumerate and access files on the compromised system. The impact extends beyond simple information disclosure to potentially enable further exploitation such as code execution through access to configuration files or web application source code that may contain additional vulnerabilities.
Mitigation strategies for CVE-2017-16152 should focus on implementing proper input validation and path sanitization mechanisms within the static-html-server application. The most effective approach involves implementing strict path normalization and validation that prevents any path components containing ../ or similar traversal sequences from being processed. Organizations should ensure that all user-supplied input is properly sanitized and that file access is restricted to a predefined, secure directory. Additionally, implementing proper access controls and privilege separation can limit the damage from such vulnerabilities. The solution should include implementing a whitelist approach for allowed file paths, ensuring that the application only serves files from designated directories. This vulnerability highlights the importance of following secure coding practices and adhering to the principle of least privilege, where applications should only have access to the minimum file system resources necessary for their operation. Regular security audits and input validation testing should be implemented to prevent similar vulnerabilities from being introduced in the future.