CVE-2019-3848 in Moodle
Summary
by MITRE
A vulnerability was found in moodle before versions 3.6.3, 3.5.5 and 3.4.8. Permissions were not correctly checked before loading event information into the calendar's edit event modal popup, so logged in non-guest users could view unauthorised calendar events. (Note: It was read-only access, users could not edit the events.)
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Analysis
by VulDB Data Team • 04/02/2026
This vulnerability resides in the moodle learning management system where insufficient permission checks were implemented in the calendar module's event handling functionality. The flaw existed across multiple versions including 3.6.3, 3.5.5, and 3.4.8, representing a critical access control weakness that allowed unauthorized information disclosure. The vulnerability specifically affected the calendar's edit event modal popup feature where the system failed to validate user permissions before retrieving and displaying event data. This represents a classic privilege escalation issue where users could bypass normal access controls to view calendar events they should not have been able to access, though the scope was limited to read-only exposure rather than modification capabilities. The vulnerability aligns with CWE-285 which addresses improper authorization in software systems, specifically targeting the calendar event access control mechanisms.
The technical implementation of this flaw occurred within the calendar module's backend processing where event information was loaded into the modal popup interface without proper authentication verification. When non-guest users accessed the calendar functionality, the system did not adequately validate whether these users possessed the necessary permissions to view specific calendar events. This oversight allowed any logged-in user to potentially access calendar events that were restricted to particular user groups or roles within the moodle environment. The vulnerability exploited the lack of proper input validation and access control checks in the calendar event retrieval process, creating an information disclosure channel that could expose sensitive educational calendar data. The issue was particularly concerning as it affected the core calendar functionality that many educational institutions rely upon for scheduling and event management.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially compromise educational institution data privacy and security. Attackers could exploit this weakness to gain insights into academic schedules, administrative events, or other sensitive calendar information that might reveal patterns in institutional operations or personal details of students and staff. While the vulnerability did not permit modification of calendar events, the ability to read unauthorized calendar information could enable social engineering attacks or provide attackers with valuable intelligence for planning further exploits. The exposure of calendar events could reveal sensitive information such as exam schedules, administrative meetings, or special events that might otherwise be restricted to specific user groups. This vulnerability particularly affects educational institutions where calendar data often contains personal and institutional information that should remain confidential.
Organizations should immediately upgrade to the patched versions of moodle 3.6.3, 3.5.5, and 3.4.8 to resolve this access control vulnerability. System administrators should conduct thorough audits of calendar event permissions and review user access controls to ensure that appropriate restrictions are in place. The vulnerability demonstrates the importance of implementing proper input validation and access control checks in web applications, particularly in modules that handle sensitive user data. Security teams should also monitor for any unusual access patterns in calendar modules and implement additional logging to track calendar event access. This vulnerability serves as a reminder of the critical need for regular security assessments and timely patch management. The flaw aligns with ATT&CK technique T1068 which involves privilege escalation through improper access control mechanisms, emphasizing the need for robust authorization checks in all application components. Organizations should also consider implementing network segmentation and additional monitoring controls around calendar and scheduling modules to detect potential exploitation attempts.