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CVE-2026-45122

MyBB: Insufficient permission check for calendar event move

Published: Aug 18, 2026Updated: Aug 18, 2026 Sources: CVE List NVDCWE-863
4.3MEDIUM
NVD MITRE
EPSS Score
0.2%
Top 83.8%
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 validate moderation permissions for the destination calendar when moving events. A user with moderation permission for the source calendar can move an event to a calendar where the user has only viewing permission because the do_move action in calendar.php does not check canmoderateevents for the target calendar. The uniquely identifying implementation details include calendar event move, source calendar moderation permission, and destination calendar viewing permission. This issue is fixed in version 1.8.40.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:NI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
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/commit/86ed2058e7f9a2c14828e731f684e997f9bb220c
github.com
https://github.com/mybb/mybb/releases/tag/mybb_1840
github.com
https://github.com/mybb/mybb/security/advisories/GHSA-839m-gpw8-59j4
github.com
and 1 more references View all →

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