CVE-2026-47245: MyBB: Buddy list corruption
MyBB is free and open source forum software. Prior to 1.8.40, the User CP Buddy/Ignore List component does not validate reciprocal buddy-list updates correctly. The usercp.php?action=doeditlists delete handler removes the selected entry from the acting user's list and then updates mybbusers.buddylist for the target account. The reciprocal update searches for the deleted target UID instead of the acting user's UID and uses the unchecked arraysearch() return value as an array key. A false result can be converted to index 0, removing the target account's first stored buddy while leaving the actual reciprocal entry unchanged. The uniquely identifying implementation details include false converted to index 0. This issue is fixed in version 1.8.40.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
MyBBto a version that resolves this vulnerability.Fixed in 1.8.40
Event History
Frequently Asked Questions
What level of access does an attacker need?
Exploitation requires an authenticated user with permission to edit their Buddy/Ignore List. No user interaction is required, and the vulnerable handler is reachable over the network.
What is the practical impact of successful exploitation?
The issue can remove the first buddy stored in the target user's buddy list when the reciprocal-entry lookup fails. It does not provide confidentiality impact or availability impact in the supplied severity assessment.
What version contains the fix?
Upgrade MyBB to version 1.8.40, which fixes the reciprocal buddy-list update logic.