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

Quick assessment

Affected
SimpleMachines SMF
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

simplemachines smf是simplemachines团队开源的一套论坛软件。 Simple Machines Forum 2.1.8之前版本和3.0 Alpha 5之前版本存在授权问题漏洞，该漏洞源于Sources/Actions/AttachmentApprove.php中存在授权绕过问题，由于单字符操作符错误导致权限检查始终通过，可能导致经过身份验证的低权限用户批准、拒绝或删除任何版块中的待处理附件，绕过自身上传的审核队列，以及枚举和删除其他用户的待处理附件。

CVSS 7.1 · High EPSS 0.47% · P38

Affected Version Matrix 4

VendorProduct Version RangeStatus
SimpleMachines SMF 2.1.0≤ 2.1.7 affected
7d048f8d66aab9af51cd6ee110fbad103cf673e8 unaffected
3.0.0 affected
a7875e876a647572dd4c45da881b875092caac3d unaffected
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I. Basic Information for CVE-2026-39903

Vulnerability Information
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Vulnerability Title
Simple Machines Forum Authorization Bypass via AttachmentApprove.php
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Simple Machines Forum 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
simplemachines smf是simplemachines团队开源的一套论坛软件。 Simple Machines Forum 2.1.8之前版本和3.0 Alpha 5之前版本存在授权问题漏洞，该漏洞源于Sources/Actions/AttachmentApprove.php中存在授权绕过问题，由于单字符操作符错误导致权限检查始终通过，可能导致经过身份验证的低权限用户批准、拒绝或删除任何版块中的待处理附件，绕过自身上传的审核队列，以及枚举和删除其他用户的待处理附件。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
SimpleMachines SMF 2.1.0 ~ 2.1.7 -

II. Public POCs for CVE-2026-39903

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 15276 chars
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In-depth vulnerability mechanism
Trigger conditions & impact
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Exploit chain & mitigation
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III. Intelligence Information for CVE-2026-39903

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Patches & Fixes for CVE-2026-39903 (4)

Vendor Advisories for CVE-2026-39903 (1)

IV. Related Vulnerabilities

Same product: SMF
Same vendor: SimpleMachines
Same weakness: CWE-863

V. Comments for CVE-2026-39903

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