CVE-2011-4592 in Moodle
Summary
by MITRE
The command-line cron implementation in Moodle 2.0.x before 2.0.6 and 2.1.x before 2.1.3 does not properly interact with IP blocking, which might allow remote attackers to bypass intended IP address restrictions by leveraging a configuration in which IP blocking was disabled to restore cron functionality.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability described in CVE-2011-4592 represents a critical security flaw in the command-line cron implementation of Moodle learning management systems. This issue affects versions 2.0.x prior to 2.0.6 and 2.1.x prior to 2.1.3, where the cron job execution mechanism fails to properly enforce IP address restrictions that are typically in place to prevent unauthorized access. The flaw stems from the improper interaction between the cron execution process and the IP blocking functionality, creating a potential bypass mechanism that could be exploited by remote attackers.
The technical nature of this vulnerability lies in the design flaw where the cron implementation does not adequately validate or enforce IP restrictions during command-line execution. When IP blocking is disabled to restore cron functionality, the system fails to maintain proper access controls, allowing unauthorized users to execute cron jobs that would normally be restricted based on IP addresses. This creates a scenario where attackers can leverage the legitimate cron execution mechanism to bypass intended security measures. The vulnerability specifically impacts the interaction between the cron daemon and the access control system, where the system's configuration logic does not properly account for the security implications of disabling IP restrictions for operational purposes.
From an operational standpoint, this vulnerability poses significant risks to Moodle deployments that rely on IP-based access controls for security. Attackers could potentially execute malicious cron jobs or gain unauthorized access to system resources by exploiting the bypass mechanism. The impact extends beyond simple access control bypass as it could enable more sophisticated attacks including privilege escalation, data exfiltration, or system compromise. Organizations using affected Moodle versions may experience unauthorized cron job execution, potentially leading to system instability, data integrity issues, or complete system compromise depending on the permissions granted to the cron processes.
The vulnerability aligns with CWE-284, which addresses improper access control in software systems, and demonstrates how configuration management flaws can create security vulnerabilities. From an attacker's perspective, this vulnerability maps to ATT&CK technique T1059.007 for command and script interpreter, as it allows for unauthorized execution of command-line processes. The flaw also relates to T1078.004 for valid accounts, as it may enable attackers to leverage legitimate cron execution mechanisms to maintain persistence. Organizations should implement immediate mitigations including upgrading to patched versions, reviewing cron job configurations, and ensuring proper IP restriction enforcement. The remediation process should include comprehensive security audits of cron job implementations and access control mechanisms to prevent similar configuration-related vulnerabilities from occurring in other system components.