CVE-2009-4816 in The Uploader
Summary
by MITRE
Directory traversal vulnerability in api/download_checker.php in MegaLab The Uploader 2.0 allows remote attackers to read arbitrary files via a .. (dot dot) in the filename parameter.
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Analysis
by VulDB Data Team • 09/09/2025
The directory traversal vulnerability identified as CVE-2009-4816 affects MegaLab The Uploader 2.0 software, specifically within the api/download_checker.php component. This flaw represents a critical security weakness that enables remote attackers to access files outside the intended directory structure through manipulation of the filename parameter. The vulnerability stems from inadequate input validation and sanitization mechanisms that fail to properly restrict directory navigation sequences.
The technical implementation of this vulnerability occurs when the application processes user-supplied filename parameters without sufficient sanitization measures. When an attacker submits a filename parameter containing .. (dot dot) sequences, the application fails to properly validate or filter these path traversal characters. This allows the attacker to navigate upward through the directory structure and access files that should remain protected. The vulnerability specifically targets the api/download_checker.php file which handles file download operations and lacks proper path validation before processing file requests.
From an operational impact perspective, this vulnerability presents significant risks to system security and data integrity. Remote attackers can potentially access sensitive files including configuration data, database credentials, application source code, and other confidential information stored on the server. The vulnerability enables unauthorized data access that could lead to complete system compromise, data exfiltration, and potential lateral movement within network environments. Organizations using MegaLab The Uploader 2.0 are exposed to risks of intellectual property theft, regulatory compliance violations, and reputational damage.
The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. This weakness allows attackers to access files and directories outside of the intended scope through manipulation of input parameters. The ATT&CK framework categorizes this as a technique under T1083 - File and Directory Discovery, where adversaries attempt to enumerate file systems and locate sensitive data. The vulnerability also relates to T1566 - Phishing with Social Engineering, as attackers may leverage this weakness to obtain sensitive information that could be used for further attacks.
Mitigation strategies should include immediate implementation of input validation and sanitization for all user-supplied parameters, particularly those related to file operations. Organizations should employ proper path validation techniques that reject or normalize path traversal sequences before processing file requests. The application should enforce strict file access controls and implement proper authorization mechanisms to ensure users cannot access files outside their designated directories. Additionally, deploying web application firewalls and implementing security headers can provide additional layers of protection. Regular security updates and patches should be applied to address known vulnerabilities, and comprehensive security testing including penetration testing should be conducted to identify similar weaknesses in the application's codebase.