CVE-2006-4937 in Moodle
Summary
by MITRE
lib/setup.php in Moodle before 1.6.2 sets the error reporting level to 7 to display E_WARNING messages to users even if debugging is disabled, which might allow remote authenticated users to obtain sensitive information by triggering the messages.
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Analysis
by VulDB Data Team • 08/04/2018
The vulnerability described in CVE-2006-4937 affects Moodle versions prior to 1.6.2 and resides within the lib/setup.php file where the error reporting level is explicitly set to 7. This configuration choice represents a critical security flaw that directly violates the principle of least privilege and information hiding. The error reporting level 7 in PHP corresponds to E_ALL & ~E_NOTICE, which means all errors except notices are displayed to end users. This behavior creates an information disclosure risk that can be exploited by authenticated attackers who are capable of triggering specific error conditions within the application's codebase.
The technical implementation of this vulnerability stems from the hardcoded error reporting level setting in the core application setup file. When Moodle initializes, it indiscriminately configures the PHP error reporting mechanism to display warnings to users regardless of the debugging configuration status. This design flaw allows attackers to manipulate application behavior through crafted requests or by exploiting existing vulnerabilities to trigger warning messages that reveal sensitive system information. The vulnerability specifically impacts authenticated users who can leverage their access privileges to cause the application to generate error conditions that expose internal details such as file paths, database structures, or other system information that should remain hidden from end users.
From an operational perspective, this vulnerability creates significant risk for Moodle deployments as it enables attackers to gather intelligence that could be used for further exploitation. The information disclosure occurs even when debugging is explicitly disabled, which means that administrators cannot rely on the standard debugging configuration to prevent this exposure. Attackers can trigger warning messages by performing actions that cause PHP to generate E_WARNING level errors, potentially revealing database connection details, file system locations, or other sensitive data that could facilitate more sophisticated attacks. This vulnerability particularly affects the security posture of educational institutions that rely on Moodle for learning management, as it provides unauthorized access to information that could compromise the entire system infrastructure.
The security implications of this vulnerability align with CWE-200, which addresses "Information Exposure" and specifically covers situations where applications inadvertently disclose sensitive information. Additionally, this issue relates to ATT&CK technique T1212, "Exploitation for Credential Access," as the leaked information could potentially be used to facilitate credential theft or privilege escalation attacks. The vulnerability also demonstrates poor security configuration management practices and violates fundamental security principles regarding the separation of concerns between development and production environments. Organizations should note that this vulnerability represents a failure in the security hardening process and underscores the importance of proper error handling and configuration management in web applications.
Mitigation strategies for this vulnerability require immediate application updates to Moodle 1.6.2 or later versions where the error reporting level is properly managed according to the debugging configuration. Administrators should also implement comprehensive monitoring of error reporting behavior and ensure that all production environments have appropriate debugging settings disabled. The fix typically involves modifying the error reporting level setting in lib/setup.php to respect the debugging configuration or to use a more restrictive error reporting level that does not expose sensitive information to end users. Security teams should also conduct thorough reviews of error handling mechanisms across all application components to prevent similar information disclosure issues and establish proper logging practices that do not inadvertently expose system details to unauthorized users.