CVE-2006-3070 in Zeroboard
Summary
by MITRE
write_ok.php in Zeroboard 4.1 pl8, when installed on Apache with mod_mime, allows remote attackers to bypass restrictions for uploading files with executable extensions by uploading a .htaccess file that with an AddType directive that assigns an executable module to files with assumed-safe extensions, as demonstrated by assigning the txt extension to be handled by application/x-httpd-php.
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Analysis
by VulDB Data Team • 07/29/2018
The vulnerability described in CVE-2006-3070 represents a sophisticated file upload restriction bypass mechanism targeting the Zeroboard content management system version 4.1 pl8. This flaw specifically exploits the interaction between the web application's file upload functionality and the Apache web server's mod_mime module, creating a pathway for attackers to execute arbitrary code through seemingly benign file uploads. The vulnerability stems from the application's inadequate validation of file types and extensions, allowing malicious actors to circumvent security controls that should prevent uploading of potentially dangerous file formats.
The technical exploitation involves a two-stage attack methodology where the attacker first uploads a specially crafted .htaccess file to the server. This configuration file leverages Apache's mod_mime module capabilities to redefine how the server handles specific file extensions. By using the AddType directive within the .htaccess file, the attacker can associate extensions that are typically considered safe, such as .txt, with executable modules like application/x-httpd-php. This manipulation effectively transforms any file with a .txt extension into an executable PHP script, bypassing the application's intended security restrictions that would normally prevent uploading of PHP files or other potentially dangerous extensions.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables full remote code execution capabilities on the affected server. Attackers can upload malicious files that will be processed by the web server's PHP interpreter, potentially leading to complete system compromise, data exfiltration, or deployment of backdoors. This vulnerability particularly affects environments where Zeroboard is deployed on Apache servers with mod_mime enabled, making it a significant concern for web application security. The attack vector demonstrates a classic example of insecure file upload handling that aligns with CWE-434, which describes the weakness of allowing files to be uploaded to a web server that can be executed by the web server.
From a defensive perspective, this vulnerability highlights the critical importance of proper input validation and the dangers of relying solely on file extension checks. The recommended mitigations include implementing comprehensive file type validation that goes beyond simple extension checking, using content-based file type detection, and restricting the ability of users to upload configuration files like .htaccess. Organizations should also consider implementing proper file upload restrictions, such as storing uploaded files outside the web root, using randomized filenames, and implementing proper access controls. The vulnerability's characteristics align with techniques documented in the MITRE ATT&CK framework under the T1190 category for Exploit Public-Facing Application, emphasizing the need for robust web application security controls and regular security assessments to identify similar bypass mechanisms.
This particular vulnerability represents a fundamental flaw in the application's security model where the system fails to properly validate file content and execution context. The exploitation demonstrates how attackers can leverage legitimate web server configuration features to subvert security controls, making it a prime example of how seemingly benign features can become security risks when not properly secured. The vulnerability's persistence across multiple versions of the software indicates a systemic issue in the application's approach to file handling and security, requiring comprehensive code review and security hardening efforts to prevent similar issues in other applications.