CVE-2006-5191 in phpBB
Summary
by MITRE
PHP remote file inclusion vulnerability in includes/functions_static_topics.php in the Nivisec Static Topics module for phpBB 1.0 and earlier 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 • 04/23/2026
The vulnerability described in CVE-2006-5191 represents a critical remote file inclusion flaw within the Nivisec Static Topics module for phpBB versions 1.0 and earlier. This issue stems from improper input validation and sanitization mechanisms that fail to properly restrict user-supplied data from being directly incorporated into file inclusion operations. The vulnerability specifically affects the functions_static_topics.php file where the phpbb_root_path parameter is processed without adequate security controls, creating an avenue for malicious actors to inject arbitrary URLs that can be executed within the phpBB environment.
The technical exploitation of this vulnerability occurs through the manipulation of the phpbb_root_path parameter which is used to determine the root path for various phpBB operations. When an attacker can control this parameter through user input, they can inject a malicious URL that points to remote code hosted on an attacker-controlled server. The vulnerability is classified as a remote file inclusion (RFI) issue, which allows attackers to execute arbitrary PHP code on the target system by leveraging the web server's file inclusion mechanisms. This type of vulnerability falls under CWE-88, which describes improper neutralization of special elements used in an OS command, and more specifically relates to CWE-94, which covers inadequate control of generation of code.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with complete control over the affected phpBB installation. Successful exploitation enables remote code execution, allowing attackers to upload and execute malicious files, access sensitive data, modify database contents, and potentially escalate privileges within the web server environment. The vulnerability affects not just individual forum installations but can compromise entire web server infrastructures if multiple vulnerable instances exist. Attackers can leverage this vulnerability to establish persistent backdoors, conduct data exfiltration, or use the compromised system as a launch point for further attacks within the network infrastructure.
Security mitigations for CVE-2006-5191 should focus on immediate patching and configuration hardening measures. The most effective solution involves upgrading to phpBB versions that have addressed this vulnerability through proper input validation and sanitization of user parameters. Organizations should implement proper parameter validation that rejects URLs containing suspicious patterns or protocols that could enable remote file inclusion. The principle of least privilege should be applied by configuring phpBB to restrict file inclusion operations to local paths only, disabling remote file access capabilities. Additionally, implementing web application firewalls and input validation rules that specifically block malicious URL patterns can provide additional layers of protection. From an ATT&CK framework perspective, this vulnerability maps to techniques involving remote code execution and privilege escalation, with the initial compromise occurring through the T1190 technique of exploitation of remote services and T1059 for command and scripting interpreter execution.