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CVE-2026-39903

7.1 · HIGH

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 op…

Published Jul 10, 2026CWE-863EPSS 0.47%

Overview

CVE-2026-39903 is a high-severity vulnerability. It was published on July 10, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/SimpleMachines/SMF/commit/7d048f8d66aab9af51cd6ee110fbad103cf673e8GitHubgithub.com/SimpleMachines/SMF/commit/a7875e876a647572dd4c45da881b875092caac3dGitHubgithub.com/SimpleMachines/SMF/pull/9181GitHubgithub.com/SimpleMachines/SMF/pull/9182Refwww.vulncheck.com/advisories/simple-machines-forum-authorization-bypass-via-attachmentapprove-php

How CyberStrike helps

Frequently asked questions

What is CVE-2026-39903?

CVE-2026-39903 is a high-severity vulnerability. It was published on July 10, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

How severe is CVE-2026-39903?

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-39903?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-39903?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-39903 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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