CVE-2006-5411 in FreeWPS
Summary
by MITRE
Unrestricted file upload vulnerability in upload.php for Free Web Publishing System (FreeWPS), possibly 2.11 and earlier, allows remote attackers to upload and execute arbitrary PHP programs.
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Analysis
by VulDB Data Team • 04/25/2026
The vulnerability identified as CVE-2006-5411 represents a critical unrestricted file upload flaw within the Free Web Publishing System version 2.11 and earlier. This vulnerability resides in the upload.php component of the web application, which fails to implement proper validation mechanisms for file uploads. The flaw enables remote attackers to bypass security restrictions and upload malicious files directly to the web server, potentially leading to complete system compromise. The vulnerability falls under the category of CWE-434, which specifically addresses Unrestricted Upload of File with Dangerous Type, a well-documented weakness in web application security frameworks. This weakness is particularly dangerous because it directly enables the execution of arbitrary code on the target system, making it a prime target for attackers seeking persistent access to web servers.
The technical implementation of this vulnerability stems from inadequate input validation within the file upload functionality. The upload.php script does not properly verify file extensions, content types, or file signatures before processing uploads. Attackers can exploit this by crafting malicious PHP files with extensions such as .php, .php3, or .phtml, which are then executed by the web server when accessed through the browser. The vulnerability also lacks proper file type checking mechanisms, allowing attackers to upload files with potentially harmful content such as web shells, backdoors, or other malicious scripts. This flaw directly violates fundamental security principles of least privilege and input sanitization, as the application fails to enforce proper access controls on the upload functionality. The vulnerability's impact is amplified by the fact that the FreeWPS system was designed for web publishing, meaning that the upload functionality was intended to be accessible to users, creating an inherent security risk when proper validation is omitted.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with complete control over the affected web server. Once a malicious file is successfully uploaded and executed, attackers can establish persistent backdoors, steal sensitive data, modify web content, or use the compromised server as a launchpad for further attacks within the network. The vulnerability enables a wide range of attack vectors including remote code execution, privilege escalation, and data exfiltration. From an attacker's perspective, this vulnerability maps directly to the MITRE ATT&CK framework's T1190 - Exploit Public-Facing Application, where attackers leverage publicly accessible web applications to gain initial access. The compromised system can be used for various malicious activities including hosting phishing sites, conducting distributed denial-of-service attacks, or serving as a command and control server for other compromised systems. The long-term operational consequences include potential data breaches, regulatory compliance violations, and significant reputational damage to organizations that fail to patch this vulnerability.
Mitigation strategies for CVE-2006-5411 must address both immediate remediation and long-term security improvements. The primary solution involves implementing strict file validation mechanisms that check file extensions, MIME types, and file content against a whitelist of approved formats. Organizations should employ multiple layers of defense including server-side validation, file type checking, and content analysis to prevent malicious uploads. The upload.php script must be modified to reject files with dangerous extensions and to verify that uploaded files are legitimate web content rather than executable scripts. Security measures should include implementing proper file permissions, restricting upload directories from direct web access, and using secure file naming conventions to prevent predictable file paths. Organizations should also implement web application firewalls to detect and block suspicious upload attempts, along with regular security audits and penetration testing to identify similar vulnerabilities. Additionally, the system should enforce proper access controls to limit who can upload files, implement logging and monitoring of upload activities, and ensure that all web applications are kept up to date with security patches. The remediation process should also include education of developers on secure coding practices, particularly around file handling and input validation, to prevent similar vulnerabilities from being introduced in future code development cycles.