CVE-2026-45126: Mybb

Low severity, CVSS 3.5. EPSS: 0.2% chance of exploitation in the next 30 days.

MyBB is free and open source forum software. Prior to 1.8.40, the Admin CP Security Questions module does not validate the anti-CSRF token correctly, allowing same-site attackers to enable or disable registration challenge questions with a specially crafted URL. The controller processes GET requests for the disable and enable actions to modify mybb_questions.active without verifying the my_post_key token attached by the user interface. The uniquely identifying implementation details include admin/modules/config/questions.php. This issue is fixed in version 1.8.40.

Affected products

• Mybb Mybb: before 1.8.40 (fixed in 1.8.40)

Published 2026-08-18. Last modified 2026-09-08.