CVE-2007-2742 in w2box
Summary
by MITRE
Unrestricted file upload vulnerability in labs.beffa.org w2box 4.0.0 Beta4 allows remote attackers to upload arbitrary PHP code via a filename with a double extension such as .php.jpg.
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Analysis
by VulDB Data Team • 09/02/2018
The vulnerability identified as CVE-2007-2742 represents a critical unrestricted file upload flaw within the w2box 4.0.0 Beta4 content management system hosted on labs.beffa.org. This vulnerability stems from inadequate input validation and file extension checking mechanisms that fail to properly sanitize user-supplied filenames. The flaw specifically manifests when the application accepts files with double extensions such as .php.jpg, allowing attackers to bypass security measures that might only check for single extensions. This type of vulnerability falls under the category of CWE-434 Unrestricted Upload of File with Dangerous Type, which is classified as a high-severity issue in the Common Weakness Enumeration framework.
The technical implementation of this vulnerability exploits the way the application processes file uploads by relying on simple string matching or basic extension validation rather than comprehensive file type verification. When an attacker uploads a file with a double extension, the system may incorrectly identify the file as an image based on the second extension while actually executing the PHP code contained within the first extension. This occurs because many web applications perform extension checks on the entire filename rather than validating the actual file content or using more sophisticated file type detection methods. The vulnerability demonstrates a fundamental flaw in the application's security architecture where trust is placed in the client-side filename rather than implementing robust server-side validation.
From an operational perspective, this vulnerability enables remote attackers to execute arbitrary PHP code on the target server with the privileges of the web application. The impact extends beyond simple code execution to include potential full system compromise, data exfiltration, and establishment of persistent backdoors. Attackers can upload malicious files that contain web shells, reverse shells, or other malicious payloads that can be triggered through subsequent web requests. The vulnerability also poses significant risks to the integrity of the entire web application and the underlying server infrastructure. According to the MITRE ATT&CK framework, this vulnerability maps to T1190 Exploit Public-Facing Application and T1059 Command and Scripting Interpreter, as it enables attackers to execute commands through the uploaded PHP code.
The mitigation strategies for this vulnerability require a multi-layered approach to file upload security. Organizations should implement strict file type validation using content-based detection rather than relying solely on filename extensions, employ proper file name sanitization techniques, and utilize secure file storage practices. The recommended defenses include validating file content using magic number detection, implementing whitelisting of allowed file types, and ensuring proper file permissions and isolation. Additionally, the application should implement comprehensive logging and monitoring of file upload activities to detect suspicious behavior. The fix involves modifying the application code to properly validate file extensions, check file content type, and implement proper sanitization of uploaded filenames. Security patches should also include implementing proper input validation at multiple layers and ensuring that uploaded files are stored in a location that is not directly accessible via web requests. This vulnerability underscores the importance of defense-in-depth strategies and proper security testing throughout the software development lifecycle to prevent such critical flaws from reaching production environments.