CVE-2026-45120

MyBB: Insufficient authorization for private calendar events

5.4 Medium

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.30%Up 0.3 points since Jun 12, 2026

What each source reports

CVE List Score used 5.4

MyBB: Insufficient authorization for private calendar events

Record: CVE-2026-45120
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-639
Updated: 2026-11-02

EUVDEUVD-2026-61017 5.4

Record: EUVD-2026-61017
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Updated: 2026-11-02

NVD 5.4

Record: CVE-2026-45120
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-639
Updated: 2026-11-02

OSV 5.4

MyBB: Insufficient authorization for private calendar events

Record: CVE-2026-45120
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-639
Updated: 2026-11-02

Affected products

mybb

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-45120 is a medium vulnerability (CVSS 5.4) in Mybb, published August 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.30%, the 23rd percentile. No source names a fixed version.