CVE-2006-5426 in LoCal Calendar System
Summary
by MITRE
PHP remote file inclusion vulnerability in lib/lcUser.php in LoCal Calendar System 1.1 remote attackers to execute arbitrary PHP code via a URL in the LIBDIR parameter.
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Analysis
by VulDB Data Team • 04/25/2026
The CVE-2006-5426 vulnerability represents a critical remote file inclusion flaw in the LoCal Calendar System version 1.1 that exposes the application to arbitrary code execution attacks. This vulnerability specifically affects the lib/lcUser.php file where the LIBDIR parameter is improperly validated and processed, allowing malicious actors to inject and execute arbitrary PHP code on the target server. The flaw stems from the application's failure to properly sanitize user input before using it in file inclusion operations, creating an attack vector that can be exploited by remote threat actors without authentication requirements.
The technical implementation of this vulnerability falls under the Common Weakness Enumeration category CWE-88, which describes improper neutralization of special elements used in an input command, specifically in the context of file inclusion operations. The vulnerability operates by accepting a URL parameter through the LIBDIR variable and directly incorporating it into a require or include statement without proper validation or sanitization. This creates a classic remote file inclusion (RFI) attack scenario where an attacker can supply a malicious URL that points to attacker-controlled PHP code, which then gets executed on the vulnerable server with the privileges of the web application.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise and data exfiltration capabilities. An attacker exploiting this vulnerability can gain persistent access to the server, potentially leading to full system control, data theft, or use of the compromised system as a launching point for further attacks within the network. The vulnerability affects the web application's authentication and authorization mechanisms, as it allows unauthenticated remote code execution, which violates fundamental security principles of access control and privilege management. This type of vulnerability also aligns with ATT&CK technique T1190, which describes the use of remote access tools and techniques to maintain persistent access to compromised systems.
Mitigation strategies for CVE-2006-5426 must address both immediate remediation and long-term security hardening measures. The primary fix involves implementing proper input validation and sanitization of the LIBDIR parameter to prevent inclusion of external URLs or unauthorized file paths. Developers should implement whitelisting approaches that restrict file inclusion to predefined, trusted directories and files. Additionally, the application should be configured to disable remote file inclusion features entirely by setting the allow_url_include directive to off in php.ini configuration files. Security hardening measures should include regular security updates, input validation libraries, and comprehensive code reviews to prevent similar vulnerabilities in future development cycles. Organizations should also implement network segmentation and monitoring to detect and prevent exploitation attempts, while following secure coding practices that align with OWASP Top Ten security guidelines to prevent injection vulnerabilities in web applications.