CVE-2026-43621: Simplemachines Smf

High severity, CVSS 8.1. EPSS: 0.4% chance of exploitation in the next 30 days.

Simple Machines Forum (SMF) through 2.1.7, fixed in commit 6f0dc61, contains an authorization state-confusion vulnerability in the profile loader that allows authenticated low-privileged users to gain administrator access by supplying multiple values for the user parameter. Attackers can exploit the mismatch between Profile::$member and User::$me->is_owner during sequential profile loading to be treated as the owner of an administrator profile, enabling unauthorized password changes and full account takeover.

Affected products

• Simplemachines Smf: up to and including 2.1.7

Published 2026-08-26. Last modified 2026-09-24.