CVE-2017-16170 in liuyaserver
Summary
by MITRE
liuyaserver is a static file server. liuyaserver 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 liuyaserver static file server vulnerability represents a critical directory traversal flaw that exposes systems to unauthorized filesystem access. This vulnerability allows attackers to manipulate URL parameters by inserting "../" sequences to navigate beyond the intended directory boundaries and access restricted files. The flaw stems from inadequate input validation and path sanitization within the server's request handling mechanism, creating a pathway for arbitrary file access that can compromise system integrity and data confidentiality.
This directory traversal vulnerability falls under the Common Weakness Enumeration category CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory. The attack vector leverages the server's failure to properly validate and sanitize user-supplied input before processing file requests. When the server processes URLs containing directory traversal sequences, it fails to normalize or validate the paths, allowing malicious actors to traverse the filesystem hierarchy and potentially access sensitive system files, configuration data, or user information. The vulnerability operates at the application layer and can be exploited through simple HTTP requests without requiring special privileges or authentication.
The operational impact of this vulnerability extends beyond simple unauthorized file access to encompass potential system compromise and data exfiltration. An attacker could leverage this flaw to access critical system files including configuration files, database credentials, application source code, or other sensitive data stored outside the designated web root directory. The vulnerability can result in complete system compromise when combined with other attack vectors, as it provides attackers with the ability to read files that may contain authentication tokens, cryptographic keys, or other sensitive information. This type of vulnerability aligns with ATT&CK technique T1083, which covers discovering file and directory permissions, and T1566, which involves initial access through spearphishing or other attack methods that can be facilitated by such traversal capabilities.
Mitigation strategies for this vulnerability require immediate implementation of proper input validation and path sanitization measures. Organizations should implement strict path validation that rejects or normalizes any input containing directory traversal sequences such as "../" or "..\". The server should enforce a whitelist approach for valid file paths or implement proper path normalization that resolves all relative paths to their canonical form before processing. Additionally, the server should operate with minimal required privileges and implement proper access controls to limit the damage even if traversal attacks succeed. Regular security audits and input validation testing should be conducted to ensure that similar vulnerabilities do not exist in other components of the system infrastructure. The remediation process should also include monitoring for suspicious access patterns and implementing logging mechanisms that can detect and alert on potential traversal attempts.