What’s Vulnerable › Vulnerabilities

CVE-2026-39903: Simple Machines Forum Authorization Bypass via AttachmentApprove.php

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-10 · updated 2026-10-25
• Weakness: CWE-863

Description

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 through 2.1.7; 3.0.0

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

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