CVE-2017-16029 in hostr
Summary
by MITRE
hostr is a simple web server that serves up the contents of the current directory. There is a directory traversal vulnerability in hostr 2.3.5 and earlier that allows an attacker to read files outside the current directory by sending `../` in the url path for GET requests.
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Analysis
by VulDB Data Team • 02/14/2020
The hostr web server vulnerability identified as CVE-2017-16029 represents a critical directory traversal flaw that fundamentally undermines the security boundaries of the application. This vulnerability affects versions 2.3.5 and earlier of the hostr web server, which is designed to serve directory contents in a simple web interface. The flaw stems from inadequate input validation and path sanitization within the application's request handling mechanism, creating an exploitable condition that allows unauthorized file access beyond the intended directory scope. The vulnerability specifically manifests when the application processes GET requests containing directory traversal sequences, enabling attackers to navigate the file system outside the designated serving directory.
The technical implementation of this vulnerability aligns with CWE-22, which classifies directory traversal attacks as a common weakness in web applications. The flaw occurs because the hostr application fails to properly sanitize URL path components before resolving file paths, allowing malicious users to manipulate the request parameters with sequences like '../' to access files outside the current directory context. When an attacker submits a request containing these traversal sequences, the web server processes them without proper validation, effectively bypassing the intended directory boundaries and exposing the underlying file system to unauthorized access. This vulnerability operates at the application layer and can be exploited through standard HTTP GET requests, making it particularly dangerous as it requires no specialized tools or techniques beyond basic web browsing capabilities.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it provides attackers with the ability to access sensitive system files, configuration data, and potentially execute malicious code if the server has access to writable directories. An attacker could exploit this vulnerability to read system configuration files, authentication credentials, database connection details, or other sensitive information that might be stored within the server's file system. The vulnerability is particularly concerning in environments where hostr servers might be deployed with elevated privileges or where sensitive data might be accessible through the file system. From an adversary perspective, this vulnerability maps to ATT&CK technique T1083, which covers the discovery of system information through directory listing and file access, and T1566, which involves the exploitation of web applications to gain unauthorized access to system resources.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements. The most effective immediate solution involves upgrading to a patched version of hostr that properly implements input validation and path sanitization techniques. Organizations should also implement proper access controls and file system permissions to limit the impact of potential exploitation, ensuring that the web server process runs with minimal required privileges. Network-level protections such as web application firewalls and intrusion detection systems can provide additional layers of defense, while application-level mitigations should include proper URL path validation, canonical path resolution, and comprehensive input sanitization. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other web applications, and the implementation of principle of least privilege should be enforced across all server components to minimize the potential damage from successful exploitation attempts.