CVE-2006-5209 in phpBB
Summary
by MITRE
PHP remote file inclusion vulnerability in admin/admin_topic_action_logging.php in Admin Topic Action Logging Mod 0.95 and earlier, as used in phpBB 2.0 up to 2.0.21, allows remote attackers to execute arbitrary PHP code via a URL in the phpbb_root_path parameter.
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Analysis
by VulDB Data Team • 04/24/2026
This vulnerability represents a critical remote file inclusion flaw that affects the phpBB bulletin board system and its associated administrative modules. The issue resides in the admin_topic_action_logging.php file within the Admin Topic Action Logging Mod version 0.95 and earlier, which is integrated into phpBB 2.0 versions up to 2.0.21. The vulnerability stems from inadequate input validation and sanitization of user-supplied parameters, specifically the phpbb_root_path parameter that is directly incorporated into file inclusion operations without proper security checks.
The technical implementation of this vulnerability occurs when an attacker can manipulate the phpbb_root_path parameter to include malicious remote files. This parameter is typically used by the administrative module to determine the root path for various operations, but due to insufficient validation, it accepts arbitrary input that can be exploited to load external PHP code. When the application processes this parameter and includes the specified path, it effectively executes any PHP code present in the remote file, providing attackers with arbitrary code execution capabilities on the affected server. This flaw directly maps to CWE-88, which describes improper neutralization of special elements used in an OS command, and more specifically to CWE-94, which covers improper control of generation of code, or Code Injection.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with complete control over the affected phpBB installation. Once exploited, attackers can execute arbitrary commands on the server, potentially leading to full system compromise, data exfiltration, or the installation of backdoors. The vulnerability affects a widely deployed forum platform, making it an attractive target for automated attacks and increasing the potential attack surface. Additionally, since this vulnerability exists in the administrative module, attackers who can access the admin interface or those who can exploit the vulnerability through other means could gain elevated privileges and access to sensitive administrative functions.
The exploitation of this vulnerability aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to code injection and remote code execution. Attackers can leverage this flaw through techniques such as web application exploitation and server-side request forgery to achieve their objectives. Organizations should implement immediate mitigations including patching to the latest stable versions of phpBB, implementing proper input validation and sanitization for all user-supplied parameters, and configuring web application firewalls to detect and block suspicious inclusion patterns. Additionally, security measures should include restricting file inclusion operations to predefined safe paths and implementing proper access controls to limit who can modify administrative parameters. The vulnerability also highlights the importance of following secure coding practices and conducting regular security assessments to identify and remediate similar flaws in web applications.