CVE-2026-45120: MyBB: Insufficient authorization for private calendar events
MyBB is free and open source forum software. Prior to 1.8.40, the calendar module does not verify private event status consistently, allowing users with viewing and moderation permissions to access and moderate private events. The private-event check used by getevents() in inc/functionscalendar.php and the event action is missing from the remaining calendar.php actions, despite the limited-access behavior described in inc/languages/english/calendar.lang.php. This issue is fixed in version 1.8.40.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
MyBB calendar moduleto a version that resolves this vulnerability.Fixed in 1.8.40
Event History
Frequently Asked Questions
Who is exposed to this issue?
MyBB installations prior to version 1.8.40 are affected if users have calendar viewing and moderation permissions. The issue concerns private calendar events and does not require an unauthenticated attacker.
What level of access does an attacker need?
An attacker needs a MyBB account with relevant calendar viewing and moderation permissions. They can then access and moderate private events because several calendar.php actions do not consistently enforce the private-event check.
What should be done if patching cannot happen immediately?
Upgrade MyBB to version 1.8.40, which fixes the inconsistent authorization checks. If an immediate upgrade is not possible, restrict calendar viewing and moderation permissions to trusted users to reduce exposure.