MyBB up to 1.8.39 Calendar functions_calendar.php get_events permission

Summaryinfo

A vulnerability was found in MyBB up to 1.8.39. It has been rated as critical. Affected is the function get_events of the file inc/functions_calendar.php of the component Calendar Module. Performing a manipulation results in permission. This vulnerability is reported as CVE-2026-45120. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability classified as critical has been found in MyBB up to 1.8.39. This affects the function get_events of the file inc/functions_calendar.php of the component Calendar Module. The manipulation with an unknown input leads to a permission vulnerability. CWE is classifying the issue as CWE-275. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

MyBB is free and open source forum software. Prior to 1.8.40, the calendar module does not verify private event status consistently, allowing users with viewing and moderation permissions to access and moderate private events. The private-event check used by get_events() in inc/functions_calendar.php and the event action is missing from the remaining calendar.php actions, despite the limited-access behavior described in inc/languages/english/calendar.lang.php. This issue is fixed in version 1.8.40.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-45120 since 05/08/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/18/2026). MITRE ATT&CK project uses the attack technique T1222 for this issue.

By approaching the search of inurl:inc/functions_calendar.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 1.8.40 eliminates this vulnerability.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Content Management System

Name

• MyBB

Version

• 1.8.0
• 1.8.1
• 1.8.2
• 1.8.3
• 1.8.4
• 1.8.5
• 1.8.6
• 1.8.7
• 1.8.8
• 1.8.9
• 1.8.10
• 1.8.11
• 1.8.12
• 1.8.13
• 1.8.14
• 1.8.15
• 1.8.16
• 1.8.17
• 1.8.18
• 1.8.19
• 1.8.20
• 1.8.21
• 1.8.22
• 1.8.23
• 1.8.24
• 1.8.25
• 1.8.26
• 1.8.27
• 1.8.28
• 1.8.29
• 1.8.30
• 1.8.31
• 1.8.32
• 1.8.33
• 1.8.34
• 1.8.35
• 1.8.36
• 1.8.37
• 1.8.38
• 1.8.39

License

• open-source

Website

• Product: https://mybb.com/

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