CVE-2019-3851 in Moodle
Summary
by MITRE
A vulnerability was found in moodle before versions 3.6.3 and 3.5.5. There was a link to site home within the the Boost theme's secure layout, meaning students could navigate out of the page.
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Analysis
by VulDB Data Team • 08/08/2023
This vulnerability exists in the moodle learning management system where the Boost theme's secure layout contains an unintended navigation link to the site home page. The flaw allows authenticated users, particularly students, to escape the intended restricted environment and access broader site navigation options. This represents a significant information disclosure and access control weakness that undermines the security boundaries designed to contain user sessions within specific course contexts. The vulnerability affects versions prior to 3.6.3 and 3.5.5, indicating it was present across multiple major release lines of the platform. The issue specifically impacts the Boost theme's implementation of secure session handling, where the navigation structure fails to properly maintain the contextual boundaries that should prevent unauthorized access to higher-level site resources.
The technical implementation flaw stems from improper session context management within the theme's layout rendering engine. When users access course pages, the Boost theme's secure layout should maintain strict navigation boundaries that prevent users from accessing site-wide navigation elements. However, the presence of a direct link to the site home page bypasses these intended security controls, creating an information leak vector. This vulnerability aligns with CWE-284 Access Control Issues, specifically concerning improper access control within user session contexts. The flaw represents a failure in the principle of least privilege as users can navigate beyond their assigned course environments to access the full site structure. This type of vulnerability falls under ATT&CK technique T1078 Valid Accounts, where legitimate user credentials are used to access unauthorized resources through application-level flaws rather than direct credential compromise.
The operational impact of this vulnerability extends beyond simple navigation issues as it enables students to potentially access course materials they shouldn't have access to, view other users' information, or even access administrative functions if the site structure allows such escalation. The vulnerability is particularly concerning in educational environments where student privacy and course confidentiality are paramount. An attacker could leverage this weakness to gather information about other courses, access shared resources, or potentially identify other users within the system. The vulnerability also undermines the trust model of the learning management system, as users can bypass the intended security boundaries that separate different course contexts. This creates an environment where unauthorized information access becomes possible through legitimate system navigation paths, making it difficult to audit user activities and maintain proper access controls. The remediation requires updating to versions 3.6.3 or 3.5.5 where the navigation structure properly maintains session boundaries and prevents unauthorized site-wide navigation from within course contexts.