CVE-2026-45120 MyBB: Insufficient authorization for private calendar events
Attackers with specific permissions can access and modify private calendar events due to missing authorization checks in the MyBB forum software.
- 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-2026-45120?
CVE-2026-45120 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 verify private event status consistently, allowing users with viewing and moderation permissions to access and moderate private events. The private-event check used by get_events() in inc/functions_calendar.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.
Weakness: CWE-639
Which versions are affected by CVE-2026-45120?
How do I fix CVE-2026-45120?
No fix has been published for CVE-2026-45120 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-2026-45120 being exploited?
There is no known exploitation of CVE-2026-45120 in the wild and no public exploit code.
Sources
Also known as GHSA-c2hm-g9w6-pv6x.