CVE-2026-45121

MyBB is free and open source forum software. Prior to 1.8.40, the calendar module does not check permissions consistently when listing calendars, allowing authenticated users to access titles of calendars that are otherwise inaccessible. The affected calendar-selection paths in calendar.php perform permission checks against an invalid calendar context before returning calendar titles. The uniquely identifying implementation details include titles of inaccessible calendars, and invalid calendar permission context. This issue is fixed in version 1.8.40.

CVSS v3 4.3 MEDIUM

4.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/mybb/mybb/commit/78e07fea34a6f6c326e668526bfb8e451c19e966
https://github.com/mybb/mybb/releases/tag/mybb_1840
https://github.com/mybb/mybb/security/advisories/GHSA-r25v-7pcm-q34p
https://mybb.com/versions/1.8.40

Configurations

No configuration.

History

No history.

Information

Published : 2026-08-18 16:17

Updated : 2026-09-08 21:02

NVD link : CVE-2026-45121

Mitre link : CVE-2026-45121

CVE.ORG link : CVE-2026-45121

JSON object : View

Products Affected

No product.

CWE

CWE-863

Incorrect Authorization

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