CVE-2008-3093 in ImperialBB
Summary
by MITRE
Unrestricted file upload vulnerability in ImperialBB 2.3.5 and earlier allows remote authenticated users to upload and execute arbitrary PHP code by placing a .php filename in the Upload_Avatar parameter and sending the image/gif content type.
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Analysis
by VulDB Data Team • 10/31/2024
The CVE-2008-3093 vulnerability represents a critical unrestricted file upload flaw in ImperialBB version 2.3.5 and earlier, exposing systems to remote code execution attacks. This vulnerability specifically affects the avatar upload functionality within the bulletin board system, creating a pathway for authenticated attackers to bypass security controls and deploy malicious code. The flaw stems from inadequate input validation and sanitization processes that fail to properly verify file extensions and content types, allowing attackers to upload PHP files disguised with legitimate image extensions.
The technical implementation of this vulnerability occurs through the Upload_Avatar parameter which does not adequately validate file types or content. Attackers can exploit this by crafting a file with a .php extension while sending the image/gif content type header, fooling the server into treating the PHP file as an image. This misclassification occurs because the application relies on content type headers rather than performing thorough file analysis or extension validation. The vulnerability directly maps to CWE-434, which addresses insecure file upload mechanisms where applications accept files without proper validation of their actual content or type. The flaw demonstrates poor input validation practices and highlights the importance of implementing multiple layers of security controls for file upload operations.
Operationally, this vulnerability enables authenticated remote attackers to execute arbitrary PHP code on the target server with the privileges of the web application. Once uploaded, the malicious PHP files can be executed directly through web requests, potentially allowing attackers to establish persistent access, escalate privileges, or exfiltrate sensitive data. The impact extends beyond immediate code execution to include potential system compromise, data breaches, and unauthorized access to user accounts within the bulletin board system. This vulnerability can be particularly dangerous in environments where the bulletin board serves as a central communication platform for organizations, as it could lead to complete system compromise and unauthorized access to sensitive information.
Mitigation strategies for CVE-2008-3093 require implementing comprehensive file upload security measures that address multiple attack vectors. Organizations should enforce strict file type validation by checking both file extensions and MIME content types against whitelists of approved formats. The system must perform thorough content analysis using tools like file signature verification rather than relying solely on headers or extensions. Implementing proper file naming conventions and storing uploaded files outside the web root directory significantly reduces the risk of execution. Additionally, enforcing proper access controls and implementing the principle of least privilege for file upload functionality helps limit potential damage. This vulnerability aligns with ATT&CK technique T1190 which covers exploiting vulnerabilities in web applications, emphasizing the need for proper input validation and secure coding practices. Organizations should also implement regular security assessments and maintain up-to-date patches for all web applications to prevent exploitation of known vulnerabilities. The remediation process should include comprehensive code review to identify similar insecure file handling patterns and ensure proper implementation of file upload security controls throughout the application architecture.