CVE-2017-16089 in serverlyr
Summary
by MITRE
serverlyr is a simple http server. serverlyr 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-2017-16089 affects serverlyr, a straightforward http server implementation that fails to properly validate user input in URL paths. This directory traversal flaw represents a critical security weakness that allows remote attackers to access arbitrary files on the server's filesystem by manipulating URL parameters through the use of directory traversal sequences such as "../". The vulnerability stems from insufficient input sanitization and path validation mechanisms within the server's request handling logic, enabling attackers to bypass normal access controls and potentially gain unauthorized access to sensitive data, configuration files, or system resources.
This security 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 attacks. The vulnerability exists at the application layer where user-supplied input is not adequately filtered or validated before being used to construct file system paths. Attackers can exploit this weakness by crafting malicious URLs that include directory traversal sequences, effectively allowing them to navigate beyond the intended document root and access files that should remain protected. The impact of such an attack can be severe, potentially exposing sensitive information including database credentials, application source code, configuration files, and other confidential data stored on the server.
The operational implications of CVE-2017-16089 extend beyond simple data exposure, as this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework under the T1083 (File and Directory Discovery) and T1566 (Phishing) tactics. An attacker who successfully exploits this vulnerability can gain comprehensive knowledge of the server's file structure, potentially leading to further exploitation opportunities including privilege escalation or lateral movement within the network. The vulnerability affects the server's integrity and confidentiality by allowing unauthorized access to files that should be restricted to authorized users only, creating potential for data breaches, intellectual property theft, and system compromise. Organizations using serverlyr or similar lightweight http servers may unknowingly expose critical system information to external threats without proper input validation mechanisms in place.
Mitigation strategies for CVE-2017-16089 should focus on implementing robust input validation and sanitization measures at the application level. The most effective approach involves implementing strict path validation that rejects any input containing directory traversal sequences or other potentially malicious path components. Organizations should ensure that all user-supplied input is properly escaped and validated before being used to construct file system paths, with additional protection mechanisms such as canonicalizing file paths and maintaining strict access controls. Security patches should be applied immediately to address the vulnerability, and the server should be configured to operate within a restricted environment with minimal necessary permissions. Additional defensive measures include implementing web application firewalls, monitoring for suspicious URL patterns, and conducting regular security assessments to identify similar vulnerabilities in other components of the system infrastructure.