CVE-2026-45122 MyBB: Insufficient permission check for calendar event move
Attackers with source calendar moderation rights can move events to calendars where they lack moderation permissions, bypassing access controls.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-45122?
CVE-2026-45122 is a medium-severity missing authorization vulnerability in mybb, published on 18 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
MyBB is free and open source forum software. Prior to 1.8.40, the calendar module does not validate moderation permissions for the destination calendar when moving events. A user with moderation permission for the source calendar can move an event to a calendar where the user has only viewing permission because the do_move action in calendar.php does not check canmoderateevents for the target calendar. The uniquely identifying implementation details include calendar event move, source calendar moderation permission, and destination calendar viewing permission. This issue is fixed in version 1.8.40.
Weakness: CWE-863
Which versions are affected by CVE-2026-45122?
How do I fix CVE-2026-45122?
No fix has been published for CVE-2026-45122 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-45122 being exploited?
There is no known exploitation of CVE-2026-45122 in the wild and no public exploit code.
Sources
Also known as GHSA-839m-gpw8-59j4.