CVE-2026-45121Network attack vector

Calendar title disclosure via invalid permission context

Published Aug 18, 2026 · Updated Aug 18, 2026

Improper access control in the calendar module in MyBB before 1.8.40 allows remote authenticated users to read restricted calendar titles. The affected calendar-selection paths in calendar.php check permissions against an invalid calendar context before returning titles, so the lookup discloses names for calendars the requester cannot otherwise access. Exploitation requires a valid account that can reach the calendar selection workflow; the issue exposes calendar titles only, with no evidence in the cited records of event-content access or modification.

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

Improper access control in the calendar module in MyBB before 1.8.40 allows remote authenticated users to read restricted calendar titles. The affected calendar-selection paths in calendar.php check permissions against an invalid calendar context before returning titles, so the lookup discloses names for calendars the requester cannot otherwise access. Exploitation requires a valid account that can reach the calendar selection workflow; the issue exposes calendar titles only, with no evidence in the cited records of event-content access or modification.

The record

CVE
CVE-2026-45121
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, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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