CVE-2017-16155 in fast-http-cli
Summary
by MITRE
fast-http-cli is the command line interface for fast-http, a simple web server. fast-http-cli is vulnerable to a directory traversal issue, giving an attacker access to the filesystem by placing "../" in the url.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/16/2020
The vulnerability identified as CVE-2017-16155 affects fast-http-cli, a command line interface component of fast-http, which is designed as a simple web server implementation. This directory traversal flaw represents a critical security weakness that allows remote attackers to access arbitrary files on the underlying filesystem through manipulation of URL paths. The vulnerability specifically manifests when the application fails to properly sanitize user-supplied input, particularly URL parameters containing directory traversal sequences.
The technical flaw stems from inadequate input validation and path resolution mechanisms within the fast-http-cli component. When a user provides a URL containing "../" sequences in the request path, the application does not properly validate or sanitize these components, allowing them to traverse up the directory structure. This behavior directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as directory traversal or path traversal vulnerabilities. The vulnerability exists at the application layer where user input is processed without sufficient sanitization, enabling attackers to bypass normal access controls and potentially access sensitive files, configuration data, or system resources that should remain protected.
From an operational perspective, this vulnerability poses significant risks to systems running affected versions of fast-http-cli. An attacker can exploit this flaw to access files outside the intended document root, potentially gaining access to sensitive information such as configuration files, database credentials, application source code, or other confidential data stored on the server. The impact extends beyond simple information disclosure, as attackers may be able to execute arbitrary code or cause system instability through careful exploitation of the traversal mechanism. The vulnerability affects the availability and confidentiality aspects of the system's security posture, making it particularly dangerous in environments where the web server hosts sensitive data or serves as a component in larger security infrastructures.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and sanitization mechanisms within the fast-http-cli application. The most effective approach involves implementing strict path validation that rejects or removes directory traversal sequences from user-supplied input before processing. Organizations should immediately update to patched versions of fast-http-cli if available, or implement application-level defenses such as canonicalizing file paths and restricting access to sensitive directories. Network-level mitigations including web application firewalls and intrusion prevention systems can provide additional protection, though these should not replace proper application-level fixes. The vulnerability also highlights the importance of following secure coding practices and implementing proper input validation as outlined in the OWASP Top Ten and NIST secure coding guidelines. Security teams should conduct comprehensive vulnerability assessments to identify other potential path traversal issues within their web applications and infrastructure components, as this type of vulnerability frequently occurs in web server implementations and can be exploited in various contexts beyond the specific fast-http-cli implementation.