CVE-2026-45120

MEDIUM 5.4

MyBB: Insufficient authorization for private calendar events

CVSS Score

5.4

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-639
Vendor	mybb
Product	mybb
Published	Aug 18, 2026
Last Updated	Aug 18, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Affected Versions

mybb / mybb

< 1.8.40

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/mybb/mybb/security/advisories/GHSA-c2hm-g9w6-pv6x github.com: https://github.com/mybb/mybb/commit/c077e6c29755187c4df78a1e674dd61bc55701b3 github.com: https://github.com/mybb/mybb/releases/tag/mybb_1840 mybb.com: https://mybb.com/versions/1.8.40