CVE-2017-16093 in cyber-js
Summary
by MITRE
cyber-js is a simple http server. A cyberjs server 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-2017-16093 affects cyber-js, a lightweight http server implementation that suffers from a critical directory traversal flaw. This issue arises from insufficient input validation and path sanitization within the server's request handling mechanism, allowing malicious actors to access arbitrary files on the underlying filesystem through carefully crafted url parameters.
The technical exploitation of this vulnerability stems from the server's failure to properly sanitize user-supplied input when processing file requests. When a client submits a request containing directory traversal sequences such as "../", the server does not adequately validate or normalize these paths before attempting to serve the requested content. This allows attackers to navigate outside the intended document root directory and access files that should remain protected, potentially exposing sensitive system information, configuration files, or user data.
This vulnerability 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 flaw represents a fundamental security oversight in the server's input processing pipeline where the application fails to implement proper path validation mechanisms. The operational impact of this vulnerability is severe as it provides attackers with unauthorized access to the entire filesystem, potentially enabling them to read system files, access sensitive configuration data, or even escalate privileges if the server process runs with elevated permissions.
The attack surface extends beyond simple file enumeration to include potential data exfiltration and system compromise. An attacker could leverage this vulnerability to access critical system files such as password hashes, configuration files, or application data that may contain credentials or other sensitive information. Additionally, the vulnerability may enable further exploitation techniques such as local file inclusion attacks or privilege escalation attempts depending on the server's execution context and the underlying operating system's security model. The impact is particularly concerning for web applications that rely on cyber-js for serving static content or as part of larger deployment architectures.
Mitigation strategies should focus on implementing proper input validation and path normalization within the server's request handling code. Organizations should ensure that all user-supplied paths are properly sanitized and validated before being processed, with explicit checks to prevent directory traversal sequences from being interpreted. The implementation should include canonicalization of file paths and enforcement of strict directory boundaries to prevent access outside the intended document root. Additionally, the server should be configured with minimal required permissions and access controls to limit the potential damage from successful exploitation attempts. Security monitoring should also be implemented to detect unusual file access patterns that may indicate exploitation attempts, and regular security updates should be applied to address similar vulnerabilities in the software supply chain.