CVE-2026-45122Network attack vector

Unauthorized event moves via unchecked destination permission

Published Aug 18, 2026 · Updated Aug 18, 2026

Authorization flaw in MyBB before 1.8.40 allows remote authenticated users to move calendar events into unauthorized calendars. In calendar.php, the do_move action checks moderation rights on the source calendar but omits a canmoderateevents check for the destination calendar before changing the event's calendar assignment. Any account that can moderate one calendar but can only view another can reposition events there, causing integrity impact without reported disclosure, deletion, or service interruption.

CVSS severity4.3
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization flaw in MyBB before 1.8.40 allows remote authenticated users to move calendar events into unauthorized calendars. In calendar.php, the do_move action checks moderation rights on the source calendar but omits a canmoderateevents check for the destination calendar before changing the event's calendar assignment. Any account that can moderate one calendar but can only view another can reposition events there, causing integrity impact without reported disclosure, deletion, or service interruption.

The record

CVE
CVE-2026-45122
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
MyBB
Product
MyBB
Classifications
CWE-863
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.8.40

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

MyBB · MyBBversion=< 1.8.40

Published CVSS scores

4.3GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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