CVE-2006-5387 in PlusXL
Summary
by MITRE
PHP remote file inclusion vulnerability in mods/iai/includes/constants.php in the PlusXL 20_272 and earlier phpBB module 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
The vulnerability described in CVE-2006-5387 represents a critical remote file inclusion flaw affecting the PlusXL 20_272 and earlier versions of a phpBB module. This vulnerability exists within the file mods/iai/includes/constants.php where the application fails to properly validate or sanitize user-supplied input. The specific parameter phpbb_root_path becomes a vector for exploitation when attackers can manipulate its value to include external URLs, thereby enabling arbitrary code execution on the target server. This type of vulnerability falls under the category of insecure direct object references and remote code execution, making it particularly dangerous for web applications that process user input without proper sanitization.
The technical implementation of this vulnerability stems from the module's reliance on user-controllable parameters to determine file inclusion paths without adequate input validation. When the phpbb_root_path parameter is passed directly to include or require statements, attackers can inject malicious URLs that point to remote servers hosting malicious PHP code. This creates an environment where remote attackers can execute arbitrary commands on the affected system, potentially leading to complete compromise of the web server. The vulnerability's impact is amplified by the fact that it affects a widely used forum platform, making it an attractive target for automated exploitation tools and malicious actors seeking to gain unauthorized access to systems.
From an operational perspective, this vulnerability presents significant risks to organizations using affected versions of the PlusXL module. The remote execution capability means that attackers can perform actions such as data exfiltration, privilege escalation, and persistence mechanisms without requiring local access to the system. The attack surface is particularly broad since phpBB installations are commonly found in environments where user-generated content is permitted, increasing the likelihood of exploitation. Security professionals should note that this vulnerability aligns with CWE-98 and CWE-88 categories, which specifically address insecure file inclusion and improper input sanitization respectively. The ATT&CK framework would classify this as a technique involving command and control through web shell deployment and remote code execution.
Mitigation strategies for this vulnerability must be implemented immediately upon identification of affected systems. The primary remediation involves upgrading to a patched version of the PlusXL module that properly validates and sanitizes the phpbb_root_path parameter before using it in file inclusion operations. Organizations should also implement input validation mechanisms that prevent URL schemes from being accepted in critical parameters, particularly those used for file path resolution. Network-level protections such as web application firewalls can provide additional defense in depth by blocking suspicious requests containing malicious URL patterns. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other modules and dependencies, as this vulnerability demonstrates the importance of proper parameter validation in web applications. System administrators must also ensure that file inclusion operations use absolute paths rather than user-controllable variables to prevent exploitation of similar vulnerabilities in other components of the application stack.