CVE-2006-5187 in Bulletin Board Ace
Summary
by MITRE
PHP remote file inclusion vulnerability in includes/functions.php in Bulletin Board Ace (BBaCE) 3.5 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 identified as CVE-2006-5187 represents a critical remote file inclusion flaw in Bulletin Board Ace version 3.5 and earlier, specifically within the includes/functions.php file. This vulnerability arises from improper input validation and sanitization of user-supplied parameters, creating an avenue for remote code execution that could compromise entire web applications. The flaw manifests when the phpbb_root_path parameter is manipulated through external URL references, allowing attackers to inject malicious PHP code that gets executed on the target server. This type of vulnerability falls under the category of CWE-88, which describes improper neutralization of special elements used in an OS command, and more specifically aligns with CWE-94, which encompasses the execution of arbitrary code or commands. The attack vector operates through the standard web application request processing where user input flows directly into server-side include operations without adequate sanitization or validation.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious URL that gets passed as the phpbb_root_path parameter to the vulnerable application. When the Bulletin Board Ace application processes this parameter, it attempts to include the specified file using PHP's include or require functions, which then executes any PHP code present in the remote file. This process bypasses normal access controls and security mechanisms, allowing the attacker to execute arbitrary commands with the privileges of the web server process. The vulnerability's severity is amplified by the fact that it requires minimal user interaction to exploit, as the malicious URL can be embedded in various attack vectors including web forms, URL parameters, or even social engineering campaigns. The inclusion of the remote file essentially creates a backdoor that can be used to establish persistent access to the compromised system.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with comprehensive control over the affected web server environment. Successful exploitation could result in complete system compromise, data theft, service disruption, or the establishment of a persistent backdoor for future access. Attackers can leverage this vulnerability to upload additional malicious files, escalate privileges, or pivot to other systems within the network. The vulnerability also poses significant risk to the integrity and confidentiality of data stored within the bulletin board system, as attackers can modify, delete, or exfiltrate sensitive information. From an attacker's perspective, this vulnerability aligns with the MITRE ATT&CK framework under the technique T1059.007 for command and script interpreter, and T1078 for valid accounts, as it allows for persistent access and execution of commands within the compromised environment. The long-term operational impact includes potential regulatory compliance violations, financial losses, and reputational damage to organizations running vulnerable versions of BBaCE.
Organizations should immediately implement multiple layers of defense to mitigate this vulnerability, beginning with the immediate upgrade to a patched version of Bulletin Board Ace or the complete removal of the vulnerable application from production environments. The recommended mitigation strategy includes implementing input validation at multiple points within the application, specifically sanitizing all user-supplied parameters before they are processed by include functions. Security measures should also incorporate the principle of least privilege by ensuring that web server processes run with minimal necessary permissions and that file inclusion operations are restricted to local directories only. Network-based defenses should include implementing web application firewalls to detect and block malicious URL patterns, while also configuring proper access controls to limit external access to application components. Additionally, regular security assessments and code reviews should be conducted to identify similar vulnerabilities in other applications, as this type of flaw often indicates broader security issues within the application architecture. The vulnerability serves as a critical reminder of the importance of secure coding practices, particularly in the handling of dynamic file inclusion operations, and underscores the necessity of implementing robust input validation mechanisms to prevent similar remote file inclusion attacks.