CVE-2026-45119
MediumCVSS 4.6Summary
Prior to version 1.8.40, the Admin CP UTF-8 Conversion module in MyBB does not validate certain requests correctly, allowing same-site attackers to alter table encoding and deny service with a specially crafted URL. The do=all control flow in admin/modules/tools/system_health.php performs ALTER TABLE operations, column rewrite phases, and fulltext index rebuilds on GET requests for the database table named by the table parameter without request verification. This issue is fixed in version 1.8.40.
Risk Assessment
Same-site attackers can alter database table encoding, potentially leading to data corruption or denial of service.
Recommendation
Upgrade MyBB to version 1.8.40 or later to add proper request validation.
Original NVD description (English source)
MyBB is free and open source forum software. Prior to 1.8.40, the Admin CP UTF-8 Conversion module does not validate certain requests correctly, allowing same-site attackers to alter table encoding and deny service with a specially crafted URL. The do=all control flow in admin/modules/tools/system_health.php performs ALTER TABLE operations, column rewrite phases, and fulltext index rebuilds on GET requests for the database table named by the table parameter without request verification. The uniquely identifying implementation details include GET requests without request verification. This issue is fixed in version 1.8.40.