CVE-2006-5289 in Vtiger
Summary
by MITRE
Multiple PHP remote file inclusion vulnerabilities in Vtiger CRM 4.2 and earlier allow remote attackers to execute arbitrary PHP code via a URL in the calpath parameter to (1) modules/Calendar/admin/update.php, (2) modules/Calendar/admin/scheme.php, or (3) modules/Calendar/calendar.php.
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Analysis
by VulDB Data Team • 04/24/2026
The vulnerability identified as CVE-2006-5289 represents a critical remote file inclusion flaw affecting Vtiger CRM versions 4.2 and earlier. This issue stems from inadequate input validation within the calendar module's administrative functions, specifically targeting three distinct entry points that process user-supplied URL parameters. The flaw allows malicious actors to inject arbitrary PHP code execution by manipulating the calpath parameter through carefully crafted URLs. This vulnerability aligns with CWE-88, which describes improper neutralization of special elements used in an eval context, and more broadly falls under CWE-94, representing improper control of generation of code. The attack vector leverages the principle of trust in user input without proper sanitization or validation, creating an environment where attacker-controlled data can be interpreted as executable code.
The technical exploitation of this vulnerability occurs when the application fails to properly validate or sanitize the calpath parameter before incorporating it into file inclusion operations. When an attacker submits a malicious URL through any of the three affected files modules/Calendar/admin/update.php, modules/Calendar/admin/scheme.php, or modules/Calendar/calendar.php, the application processes this input without adequate security controls. This allows the attacker to specify a remote URL that contains malicious PHP code, which then gets executed on the vulnerable server. The attack operates under the ATT&CK framework's technique T1190, which describes exploitation of remote services through the use of file inclusion vulnerabilities. The vulnerability essentially permits attackers to bypass normal access controls and execute arbitrary commands on the target system, potentially leading to complete system compromise.
The operational impact of CVE-2006-5289 extends far beyond simple code execution, as it provides attackers with persistent access to the vulnerable system. Once exploited, an attacker can establish backdoors, escalate privileges, and potentially move laterally within the network infrastructure. The vulnerability affects not only the calendar module but also potentially exposes the entire Vtiger CRM application to unauthorized access, as the compromised system can serve as a foothold for further attacks. Organizations using vulnerable versions face significant risks including data breaches, system compromise, and potential regulatory violations. The attack surface is particularly concerning given that calendar modules often contain sensitive business information and may be accessible to multiple users within an organization. This vulnerability demonstrates the critical importance of input validation and the principle of least privilege in web application security, as the flaw exists in administrative functions that should require strict access controls and input sanitization.
Mitigation strategies for CVE-2006-5289 require immediate action to address the root cause through proper input validation and parameter sanitization. Organizations should implement strict validation of all user-supplied input, particularly parameters used in file inclusion operations, using allowlists of acceptable values rather than denylists. The recommended approach involves updating to Vtiger CRM versions that have patched this vulnerability, as the original software versions are no longer supported and lack security updates. Security controls should include disabling remote file inclusion capabilities within the application, implementing proper input sanitization functions, and applying web application firewalls to filter malicious requests. Additionally, organizations should conduct comprehensive security assessments of their web applications to identify similar vulnerabilities that may exist in other components. The remediation process should also include implementing proper access controls and monitoring for suspicious activities that may indicate exploitation attempts. According to industry best practices and the ATT&CK framework, this vulnerability highlights the necessity of defense-in-depth strategies that combine multiple security controls to prevent successful exploitation of similar vulnerabilities.