CVE-2026-39903

Description

Simple Machines Forum 2.1 prior to 2.1.8 and 3.0 prior to 3.0 Alpha 5 contains an authorization bypass vulnerability in Sources/Actions/AttachmentApprove.php where a single-character operator error causes the permission check to always pass regardless of user permissions. An authenticated low-privileged user can approve, reject, or delete any pending attachments on any board without holding the required approve_posts permission, bypass moderation queues for their own uploads, and enumerate and delete other users' pending attachments.

References

• https://github.com/SimpleMachines/SMF/commit/7d048f8d66aab9af51cd6ee110fbad103cf673e8
• https://github.com/SimpleMachines/SMF/commit/a7875e876a647572dd4c45da881b875092caac3d
• https://github.com/SimpleMachines/SMF/pull/9181
• https://github.com/SimpleMachines/SMF/pull/9182
• https://www.vulncheck.com/advisories/simple-machines-forum-authorization-bypass-via-attachmentapprove-php