Permission Flaw in MyBB Calendar Module
CVE-2026-45121

4.3MEDIUM

Key Information:

Vendor

Mybb

Status
Mybb
Vendor
CVE Published:
18 August 2026

What is CVE-2026-45121?

The calendar module in MyBB, a popular open-source forum software, contains a permissions flaw that allows authenticated users to list titles of calendars without proper access rights. This issue arises from inconsistent permission checks in key areas of the code, allowing sensitive calendar titles to be exposed. The flaw has been addressed in version 1.8.40, reinforcing the importance of maintaining updated software to protect against unauthorized access.

Affected Version(s)

mybb < 1.8.40

References

https://github.com/mybb/mybb/security/advisories/GHSA-r25...
x_refsource_CONFIRM
https://github.com/mybb/mybb/commit/78e07fea34a6f6c326e66...
x_refsource_MISC
https://github.com/mybb/mybb/releases/tag/mybb_1840
x_refsource_MISC

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.