CVE-2017-16156 in myprolyz
Summary
by MITRE
myprolyz is a static file server. myprolyz 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-2017-16156 affects myprolyz, a static file server implementation that suffers from a critical directory traversal flaw. This security weakness allows unauthorized attackers to access arbitrary files on the server's filesystem by manipulating URL parameters through the strategic insertion of directory traversal sequences such as "../". The vulnerability stems from insufficient input validation and sanitization within the application's file serving mechanism, which fails to properly restrict path resolution operations. When a user requests a file through the web interface, the application processes the requested path without adequate verification of its legitimacy, enabling malicious actors to navigate beyond the intended document root directory. This flaw directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal vulnerabilities. The attack vector operates through simple URL manipulation where an attacker can construct malicious paths that bypass normal access controls and gain unauthorized access to sensitive system files, configuration data, or other restricted resources that should not be publicly accessible.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially enable attackers to execute arbitrary code or cause system compromise through access to critical system files, including but not limited to configuration files, database files, or system binaries. The severity of this weakness is amplified by the fact that directory traversal attacks are among the most common and well-understood exploitation techniques in cybersecurity, making this vulnerability particularly dangerous due to its ease of exploitation and the broad range of potential damage. Attackers can leverage this vulnerability to access sensitive data such as user credentials, application secrets, or system configuration information that could lead to further compromise of the affected system. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1083, which covers discovering file and directory permissions, and T1005, which involves data from local system. The vulnerability also represents a failure in the principle of least privilege, as the application does not properly enforce access controls that would prevent unauthorized path resolution operations.
Mitigation strategies for CVE-2017-16156 should focus on implementing robust input validation and sanitization mechanisms within the application's file serving components. The most effective immediate fix involves implementing proper path validation that rejects or strips out directory traversal sequences such as "../", "..\", or similar patterns from user-supplied input before processing file requests. Organizations should deploy web application firewalls or security filters that can detect and block suspicious path traversal attempts in real-time. Additionally, implementing proper access controls and ensuring that the application runs with minimal required privileges can significantly reduce the potential impact of successful exploitation attempts. Regular security auditing and code reviews should be conducted to identify similar vulnerabilities in other components of the application stack. The implementation of a secure coding framework that enforces proper path validation and sanitization should be mandatory for all file handling operations. Organizations should also consider implementing monitoring and alerting mechanisms to detect suspicious file access patterns that may indicate exploitation attempts. System administrators should regularly update and patch all components of their infrastructure, including the myprolyz application itself, to ensure that known vulnerabilities are addressed promptly. Compliance with security standards such as ISO 27001 and NIST cybersecurity frameworks should include mandatory vulnerability assessment procedures that specifically target directory traversal vulnerabilities and similar path manipulation issues.