CVE-2017-16193 in mfrs
Summary
by MITRE
mfrs is a static file server. mfrs 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-2017-16193 affects mfrs, a static file server implementation that serves files from a specified directory. This directory traversal flaw represents a critical security weakness that allows unauthorized access to the underlying filesystem through crafted URL requests. The vulnerability stems from inadequate input validation and path sanitization within the application's file serving mechanism, where user-supplied paths are not properly constrained or normalized before being processed.
This directory traversal vulnerability operates by exploiting the lack of proper path validation in the application's request handling logic. When an attacker includes "../" sequences in the URL path, the application fails to properly sanitize these inputs, allowing the traversal mechanism to navigate outside of the intended serving directory. The flaw essentially permits attackers to access files and directories that should remain protected within the server's file system hierarchy, potentially exposing sensitive data, configuration files, or system resources.
The operational impact of this vulnerability extends beyond simple file access, as it can enable attackers to escalate their privileges and potentially gain deeper system access. An attacker could leverage this weakness to retrieve system configuration files, database credentials, application source code, or other sensitive materials stored on the server. The vulnerability aligns with CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. This weakness allows attackers to access files and directories outside the intended scope of the application's file serving capabilities.
From an adversarial perspective, this vulnerability provides attackers with a straightforward method to bypass access controls and extract information from the server. The attack vector requires minimal technical expertise and can be executed through standard web browser navigation or automated tools. The impact is particularly severe in environments where the static file server is used to serve sensitive content or where the application runs with elevated privileges that could allow access to system-critical files. This vulnerability can be mapped to ATT&CK technique T1083, which covers the discovery of files and directories, as attackers can use directory traversal to enumerate and access system resources that should remain protected.
Mitigation strategies for this vulnerability involve implementing proper input validation and path normalization within the application's file serving logic. Developers should ensure that all user-supplied paths are sanitized and normalized before being processed, rejecting or removing any path traversal sequences such as "../" or "..\". The implementation should enforce strict directory boundaries and validate that requested paths remain within the intended serving directory. Additional protective measures include implementing proper access controls, using secure coding practices, and regularly updating the application to address known vulnerabilities. Organizations should also consider implementing network-level protections such as web application firewalls that can detect and block suspicious path traversal attempts, though the most effective solution remains proper code-level validation and sanitization of user inputs.