CVE-2017-16167 in yyooopack
Summary
by MITRE
yyooopack is a simple file server. yyooopack 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 vulnerability identified as CVE-2017-16167 affects yyooopack, a simple file server application that serves files over HTTP. This directory traversal vulnerability represents a critical security flaw that allows unauthorized access to the underlying filesystem through improper input validation in URL handling. The vulnerability stems from the application's failure to properly sanitize user-supplied input when processing file requests, enabling attackers to manipulate file paths through the use of directory traversal sequences.
The technical implementation of this vulnerability occurs when the yyooopack server processes URLs containing "../" sequences that are used to navigate up directory levels in the filesystem hierarchy. When an attacker crafts a malicious URL with these traversal sequences, the server fails to validate or sanitize the input properly, allowing the application to resolve file paths beyond its intended directory scope. This flaw directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as directory traversal or path traversal attacks. The vulnerability exists at the application layer where input validation mechanisms are insufficient to prevent malicious path manipulation attempts.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with unrestricted access to the server's filesystem. An attacker could potentially access sensitive files such as configuration files, database credentials, application source code, and other confidential data stored on the server. The vulnerability also enables further attack vectors including arbitrary code execution if the server allows execution of scripts or if attackers can place malicious files in writable directories. This type of vulnerability can be exploited as part of a broader attack chain that may include initial access, privilege escalation, and lateral movement within a network environment. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1059 for command and scripting interpreter and T1566 for credential access through exploitation of vulnerable applications.
Mitigation strategies for this vulnerability require immediate implementation of proper input validation and sanitization mechanisms within the yyooopack application. The most effective approach involves implementing strict path validation that ensures all file requests are confined to the intended directory scope, rejecting any requests containing directory traversal sequences. Developers should employ secure coding practices including whitelisting acceptable file paths, using absolute paths with proper directory restrictions, and implementing proper access controls for file operations. Additionally, the application should validate that resolved file paths remain within the designated root directory and reject any requests that attempt to access parent directories. System administrators should also consider implementing network-level protections such as web application firewalls and access control lists to limit exposure, while regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other applications. The remediation process should follow industry standards for secure coding practices and vulnerability management protocols to ensure comprehensive protection against similar traversal attacks.