CVE-2012-0797 in Moodle
Summary
by MITRE
The webservices functionality in Moodle 2.0.x before 2.0.7, 2.1.x before 2.1.4, and 2.2.x before 2.2.1 allows remote authenticated users to bypass the deleted status and continue using a server via a token.
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Analysis
by VulDB Data Team • 02/18/2019
The vulnerability described in CVE-2012-0797 represents a critical authorization bypass flaw within Moodle's web services implementation that affects multiple versions of the popular learning management system. This issue stems from inadequate validation of user account status within the token-based authentication mechanism used by Moodle's web services functionality. The vulnerability specifically impacts Moodle versions 2.0.x before 2.0.7, 2.1.x before 2.1.4, and 2.2.x before 2.2.1, creating a persistent security risk for organizations relying on these platforms for educational content delivery and user management.
The technical flaw manifests in how Moodle processes authentication tokens for web services when users have been marked as deleted within the system. Normally, when a user account is deleted, the system should invalidate any existing tokens associated with that user and prevent further access through web services. However, the vulnerability allows authenticated users who have been marked as deleted to continue operating within the system using valid tokens, effectively bypassing the intended deletion status checks. This occurs because the token validation process fails to properly verify whether the underlying user account status has been changed to deleted, creating a window where compromised or malicious users can maintain access to system resources beyond their intended authorization period.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally undermines the integrity of user management within Moodle's web services framework. Attackers who can obtain valid tokens from deleted accounts can potentially access sensitive educational data, manipulate course content, or perform administrative functions that should be restricted to active users only. This vulnerability particularly affects organizations that rely heavily on Moodle's web services for integration with external systems, automated processes, or mobile applications, as it creates persistent backdoors that could remain undetected for extended periods. The risk is exacerbated when considering that web services often provide programmatic access to core system functions that may not be adequately protected by traditional user interface controls.
This vulnerability aligns with CWE-284, which addresses improper access control, and demonstrates how token-based authentication systems can fail to properly validate user state changes. From an attack perspective, it corresponds to techniques described in the ATT&CK framework under privilege escalation and persistence tactics, as attackers can maintain access through valid tokens even after account deletion. The flaw represents a classic case of insufficient input validation and state management within authentication systems, where the system fails to properly synchronize the status of authentication tokens with the underlying user account status. Organizations should prioritize immediate patching of affected Moodle installations and implement additional monitoring for unauthorized token usage patterns. Security teams should also review token lifecycle management processes and ensure that account deletion procedures properly invalidate associated web service tokens to prevent similar vulnerabilities in other systems.