CVE-2006-4939 in Moodle
Summary
by MITRE
backup/backup_scheduled.php in Moodle before 1.6.2 generates trace data with the full backup pathname even when debugging is disabled, which might allow attackers to obtain the pathname.
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Analysis
by VulDB Data Team • 08/04/2018
The vulnerability identified as CVE-2006-4939 affects Moodle versions prior to 1.6.2 and specifically targets the backup_scheduled.php script within the backup module. This issue represents a sensitive data exposure vulnerability where the system inadvertently reveals critical path information through debug trace data even when debugging functionality is explicitly disabled. The flaw occurs in the scheduled backup process where the application generates detailed trace information containing the complete file system path to backup operations. This behavior violates fundamental security principles by providing attackers with potentially useful information about the underlying system architecture and file organization. The vulnerability falls under CWE-200, which addresses improper exposure of sensitive information, and demonstrates how seemingly innocuous debug features can create security risks when not properly configured or secured.
The technical implementation of this vulnerability stems from the backup_scheduled.php script's handling of error conditions and trace generation. When the backup process encounters issues or when debugging is enabled for any reason, the system logs complete file paths including directory structures and file names. Even when debugging is disabled at the application level, the trace data generation mechanism continues to include the full backup pathname in its output. This occurs because the code does not properly check the debugging state before including path information in trace logs, creating a scenario where sensitive system information becomes accessible through error messages or log entries. The flaw demonstrates poor input validation and output sanitization practices, as the system fails to distinguish between legitimate operational information and potentially harmful path disclosure.
The operational impact of this vulnerability extends beyond simple information disclosure, as the exposed path information could enable more sophisticated attacks. Attackers who gain access to the trace data could potentially use the discovered paths to understand the system's file structure, identify potential attack vectors, or craft targeted attacks against specific files or directories. The vulnerability creates opportunities for path traversal attacks, directory enumeration, and other reconnaissance activities that could lead to further system compromise. In environments where Moodle is deployed with sensitive educational or institutional data, this path disclosure could provide attackers with crucial information needed to plan more effective attacks. The vulnerability also impacts system integrity by potentially exposing backup locations that might contain confidential student records or other sensitive information. This aligns with ATT&CK technique T1083, which covers directory and file discovery, and demonstrates how information gathering can precede more serious exploitation attempts.
Mitigation strategies for this vulnerability require immediate patching of affected Moodle installations to version 1.6.2 or later, where the issue has been addressed through proper path sanitization in debug trace generation. System administrators should ensure that debugging features are properly disabled in production environments and that all trace data generation includes appropriate sanitization of sensitive information. Additional protective measures include implementing proper log monitoring to detect and alert on unexpected path disclosures, configuring file system permissions to limit access to backup directories, and conducting regular security reviews of debug and trace functionality. Organizations should also consider implementing web application firewalls that can filter out sensitive path information from response data and establish security policies that prohibit the inclusion of system paths in error messages or trace logs. The vulnerability underscores the importance of following security best practices in software development, particularly regarding the handling of sensitive information in debug and error reporting contexts.