CVE-2006-3556 in extcalendar
Summary
by MITRE
PHP remote file inclusion vulnerability in extcalendar.php in Mohamed Moujami ExtCalendar 2.0 allows remote attackers to execute arbitrary PHP code via a URL in the mosConfig_absolute_path parameter.
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Analysis
by VulDB Data Team • 10/18/2025
The CVE-2006-3556 vulnerability represents a critical remote file inclusion flaw in the ExtCalendar 2.0 web application developed by Mohamed Moujami. This vulnerability exists within the extcalendar.php script and stems from improper input validation mechanisms that fail to sanitize user-supplied parameters before incorporating them into file inclusion operations. The specific parameter mosConfig_absolute_path serves as the attack vector, where an attacker can inject malicious URLs that get processed by the application's file inclusion functions, thereby enabling unauthorized code execution on the target system. This type of vulnerability falls under the category of insecure direct object references and improper input validation as classified by CWE-22 and CWE-94 respectively.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious request containing a URL within the mosConfig_absolute_path parameter, which is then processed by the vulnerable application. The application's failure to properly validate or sanitize this input allows the remote attacker to include arbitrary PHP files from external servers, effectively enabling code execution with the privileges of the web server process. This vulnerability directly maps to the ATT&CK technique T1190 - Exploit Public-Facing Application, as it targets a publicly accessible web application component that can be exploited from remote locations without requiring authentication. The flaw demonstrates a classic case of inadequate input sanitization where user-controllable data enters the application's execution flow without proper validation, creating a pathway for malicious code injection.
The operational impact of this vulnerability is severe and far-reaching for affected organizations. Successful exploitation allows attackers to execute arbitrary code on the target system, potentially leading to complete system compromise, data exfiltration, or the establishment of persistent backdoors. Attackers can leverage this vulnerability to deploy web shells, install malware, or perform further reconnaissance activities within the network. The vulnerability affects any system running ExtCalendar 2.0 with the specific configuration that permits remote parameter injection. The risk is particularly elevated in environments where the web server has elevated privileges and where the application is accessible from untrusted networks. Organizations may face regulatory compliance violations and potential legal consequences due to unauthorized access to their systems, as this vulnerability can be exploited to gain persistent access and control over critical infrastructure.
Mitigation strategies for CVE-2006-3556 should focus on immediate patching and input validation improvements. The primary remediation involves applying the vendor-provided security patch or upgrading to a newer version of ExtCalendar that addresses this vulnerability. Organizations should implement strict input validation measures to sanitize all user-supplied parameters before they are processed by the application. This includes implementing whitelisting mechanisms for path parameters, disabling remote file inclusion features, and employing proper parameter validation techniques. Network-level defenses such as web application firewalls and intrusion prevention systems can provide additional protection against exploitation attempts. Regular security assessments and code reviews should be conducted to identify similar vulnerabilities in other components of the application stack. The vulnerability highlights the importance of following secure coding practices and adhering to security standards such as those outlined in the OWASP Top Ten and the CWE guidelines to prevent similar issues in future development cycles.