CVE-2017-16105 in serverwzl
Summary
by MITRE
serverwzl is a simple http server. serverwzl 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 • 02/15/2020
The vulnerability identified as CVE-2017-16105 affects serverwzl, a straightforward http server implementation that suffers from a critical directory traversal flaw. This security weakness allows malicious actors to access arbitrary files on the underlying filesystem by manipulating URL paths through the strategic insertion of "../" sequences. The vulnerability represents a fundamental failure in input validation and path handling within the server's file access mechanisms.
This directory traversal vulnerability stems from inadequate sanitization of user-supplied input in the URL parsing logic. When the server processes requests containing "../" sequences in the path component, it fails to properly validate or normalize these paths before attempting to access files on the filesystem. The flaw enables attackers to navigate beyond the intended document root directory and potentially access sensitive system files, configuration data, or other restricted resources that should remain isolated from external access. 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.
The operational impact of this vulnerability is significant as it provides attackers with unauthorized access to the underlying filesystem. An attacker could potentially retrieve system configuration files, user data, application source code, or other sensitive information that resides on the server. The attack surface extends beyond simple file reading to include potential privilege escalation opportunities if the server process runs with elevated permissions. This vulnerability can be exploited through simple web requests without requiring authentication, making it particularly dangerous in environments where the server is accessible to unauthenticated users.
Mitigation strategies for CVE-2017-16105 should focus on implementing robust input validation and path normalization techniques. The server implementation must properly sanitize all user-supplied paths by rejecting or removing directory traversal sequences before processing file access requests. Security measures should include canonicalizing file paths to prevent resolution of "../" sequences, implementing strict directory restrictions that limit file access to predefined safe directories, and employing proper access controls that prevent traversal beyond intended boundaries. Organizations should also consider implementing web application firewalls and input validation mechanisms that can detect and block suspicious path sequences. The vulnerability demonstrates the importance of following secure coding practices and adhering to the principle of least privilege when designing web server implementations. This issue relates to ATT&CK technique T1083, which covers discovering file and directory permissions, as the vulnerability enables unauthorized access to system resources that should remain protected.