CVE-2026-39903: Simplemachines Smf

High severity, CVSS 7.1. EPSS: 0.5% chance of exploitation in the next 30 days.

Simple Machines Forum 2.1 prior to commit 7d048f8 and 3.0 prior to commit a7875e8 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.

Affected products

• Simplemachines Smf: from 2.1.0, up to and including 2.1.7; version 3.0.0 only

Published 2026-07-10. Last modified 2026-07-14.