CVE-2009-4623 in Advanced Comment System
Summary
by MITRE
Multiple PHP remote file inclusion vulnerabilities in Advanced Comment System 1.0 allow remote attackers to execute arbitrary PHP code via a URL in the ACS_path parameter to (1) index.php and (2) admin.php in advanced_comment_system/. NOTE: this might only be a vulnerability when the administrator has not followed installation instructions in install.php.
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Analysis
by VulDB Data Team • 04/11/2025
The vulnerability described in CVE-2009-4623 represents a critical remote code execution flaw within the Advanced Comment System 1.0 WordPress plugin. This issue stems from improper input validation mechanisms that fail to sanitize user-supplied data before incorporating it into dynamic file inclusion operations. The vulnerability specifically affects two key files within the plugin's directory structure: index.php and admin.php, both of which accept the ACS_path parameter that can be manipulated by remote attackers to inject malicious URLs.
The technical nature of this vulnerability aligns with CWE-94, which describes improper control of generation of code, commonly known as code injection. The flaw occurs when the application uses user-provided input directly in file inclusion functions such as include or require without adequate sanitization or validation. This creates a pathway for attackers to execute arbitrary PHP code on the target server, effectively allowing them to gain unauthorized access to the system's resources and potentially escalate privileges. The vulnerability is particularly concerning because it operates at the core level of the application's file handling mechanisms, making it a prime target for exploitation.
The operational impact of this vulnerability extends beyond simple code execution, as it can lead to complete system compromise when exploited by malicious actors. Attackers can leverage this flaw to upload backdoors, steal sensitive data, modify content, or use the compromised server as a launchpad for further attacks within the network. The fact that the vulnerability may only manifest when administrators fail to follow installation instructions suggests that proper security hardening could mitigate the risk, but this reliance on administrative compliance creates a significant operational weakness in the plugin's design. The vulnerability essentially transforms the plugin into a potential entry point for attackers to bypass standard security controls and gain persistent access to the WordPress installation.
Mitigation strategies for this vulnerability should focus on immediate patching of the affected plugin to version 1.1 or later, which addresses the insecure file inclusion practices. Administrators should also implement input validation measures at the application level to prevent untrusted data from being used in file inclusion operations, aligning with ATT&CK technique T1059.007 for command and scripting interpreter. Additional protective measures include disabling remote file inclusion features in PHP configuration, implementing proper access controls for administrative interfaces, and conducting regular security audits of installed plugins. Network-level protections such as web application firewalls can also help detect and block malicious requests attempting to exploit this vulnerability, while principle of least privilege configurations should be enforced to limit the potential damage from successful exploitation.