CVE-2019-3847 in Moodle
Summary
by MITRE
A vulnerability was found in moodle before versions 3.6.3, 3.5.5, 3.4.8 and 3.1.17. Users with the "login as other users" capability (such as administrators/managers) can access other users' Dashboards, but the JavaScript those other users may have added to their Dashboard was not being escaped when being viewed by the user logging in on their behalf.
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Analysis
by VulDB Data Team • 08/17/2023
This vulnerability exists in the moodle learning management system where administrators or users with the specific capability to "login as other users" can access and view the dashboards of other users. The flaw specifically affects versions prior to 3.6.3, 3.5.5, 3.4.8, and 3.1.17, representing a critical security oversight in the platform's privilege management and output sanitization mechanisms. The vulnerability stems from improper handling of user-generated content within the dashboard interface, creating a cross-site scripting attack vector that can be exploited by privileged users.
The technical implementation flaw occurs when the system displays dashboard content created by one user to another user who has logged in on their behalf. When the system renders the dashboard, it fails to properly escape or sanitize the javascript code that individual users may have added to their personal dashboards. This creates a classic cross-site scripting vulnerability where malicious javascript code can be executed in the context of the privileged user's browser session, potentially allowing for session hijacking, data theft, or further exploitation of the compromised account.
The operational impact of this vulnerability is significant as it allows for privilege escalation and persistent attack vectors within the learning management system. An administrator or manager with login-as capabilities can execute arbitrary javascript code in the context of any user's session, potentially accessing sensitive course materials, user data, or even gaining access to other administrative functions. This vulnerability directly violates the principle of least privilege and can enable attackers to maintain persistent access to user accounts while remaining undetected within the system. The attack can be particularly dangerous in educational environments where users may have access to sensitive student information, grades, or personal data.
The vulnerability aligns with CWE-79 which describes cross-site scripting flaws in web applications, and represents a specific instance of CWE-116 where improper output escaping leads to code execution. From an ATT&CK framework perspective, this vulnerability maps to T1078 which covers valid accounts and T1548.001 which involves abuse of privileges, potentially leading to T1059 for command and scripting interpreter execution. The security implications extend beyond simple XSS as this vulnerability can be leveraged to create a persistent backdoor within the system, allowing attackers to maintain access even after the initial compromise. Organizations should implement immediate patching of affected versions, conduct thorough security assessments of user privileges, and consider implementing additional monitoring for suspicious login activities and dashboard modifications. The recommended mitigation includes upgrading to the patched versions, implementing proper output escaping mechanisms, and establishing strict access controls for the login-as functionality to prevent unauthorized privilege escalation.