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CVE-2026-45121

MyBB: Insufficient permission check for calendar select

Published: Aug 18, 2026Updated: Aug 18, 2026 Sources: CVE List NVDCWE-863
4.3MEDIUM
NVD MITRE
EPSS Score
0.3%
Top 83.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

Description

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:LI:NA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:LConfidentiality
Low
I:NIntegrity
None
A:NAvailability
None
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Weaknesses

CWE-863

Affected Products

mybb
oss-projectaka mybb forums
mybb
Web & CMS Plugins

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
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References

https://github.com/mybb/mybb/security/advisories/GHSA-r25v-7pcm-q34p
github.com
https://github.com/mybb/mybb/commit/78e07fea34a6f6c326e668526bfb8e451c19e966
github.com
https://github.com/mybb/mybb/releases/tag/mybb_1840
github.com
and 1 more references View all →

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