CVE-2026-45121
MediumCVSS 4.3Summary
Prior to version 1.8.40, the calendar module in MyBB does not check permissions consistently when listing calendars, allowing authenticated users to access titles of calendars that are otherwise inaccessible. The affected calendar-selection paths in calendar.php perform permission checks against an invalid calendar context before returning calendar titles. This issue is fixed in version 1.8.40.
Risk Assessment
Authenticated users may gain access to titles of private or hidden calendars, potentially exposing sensitive organizational information.
Recommendation
Upgrade MyBB to version 1.8.40 or later to remediate this vulnerability.
Original NVD description (English source)
MyBB is free and open source forum software. Prior to 1.8.40, the calendar module does not check permissions consistently when listing calendars, allowing authenticated users to access titles of calendars that are otherwise inaccessible. The affected calendar-selection paths in calendar.php perform permission checks against an invalid calendar context before returning calendar titles. The uniquely identifying implementation details include titles of inaccessible calendars, and invalid calendar permission context. This issue is fixed in version 1.8.40.