CVE-2026-39903
Simple Machines Forum Authorization Bypass via AttachmentApprove.php
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.
INFO
Published Date :
July 10, 2026, 5:16 p.m.
Last Modified :
July 14, 2026, 9:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-39903
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update Simple Machines Forum to version 2.1.8 or later.
- Update Simple Machines Forum to version 3.0 Alpha 5 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-39903.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-39903 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-39903
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-39903 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-39903 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Jul. 14, 2026
Action Type Old Value New Value Changed Affected [{'repo': 'https://github.com/SimpleMachines/SMF', 'vendor': 'SimpleMachines', 'product': 'SMF', 'versions': [{'status': 'affected', 'version': '2.1.0', 'lessThan': '7d048f8d66aab9af51cd6ee110fbad103cf673e8', 'versionType': 'git'}, {'status': 'affected', 'version': '3.0.0', 'lessThan': 'a7875e876a647572dd4c45da881b875092caac3d', 'versionType': 'git'}], 'defaultStatus': 'affected'}] [{'repo': 'https://github.com/SimpleMachines/SMF', 'vendor': 'SimpleMachines', 'product': 'SMF', 'versions': [{'status': 'affected', 'version': '2.1.0', 'versionType': 'semver', 'lessThanOrEqual': '2.1.7'}, {'status': 'unaffected', 'version': '7d048f8d66aab9af51cd6ee110fbad103cf673e8', 'versionType': 'git'}, {'status': 'affected', 'version': '3.0.0', 'versionType': 'semver'}, {'status': 'unaffected', 'version': 'a7875e876a647572dd4c45da881b875092caac3d', 'versionType': 'git'}], 'packageURL': 'pkg:github/SimpleMachines/SMF', 'defaultStatus': 'affected'}] -
CVE Modified by [email protected]
Jul. 14, 2026
Action Type Old Value New Value Changed Affected [{'repo': 'https://github.com/SimpleMachines/SMF', 'vendor': 'SimpleMachines', 'product': 'SMF', 'versions': [{'status': 'affected', 'version': '2.1.0', 'lessThan': '2.1.8', 'versionType': 'semver'}, {'status': 'affected', 'version': '3.0.0', 'lessThan': '3.0.0 Alpha 5', 'versionType': 'custom'}], 'defaultStatus': 'affected'}] [{'repo': 'https://github.com/SimpleMachines/SMF', 'vendor': 'SimpleMachines', 'product': 'SMF', 'versions': [{'status': 'affected', 'version': '2.1.0', 'lessThan': '7d048f8d66aab9af51cd6ee110fbad103cf673e8', 'versionType': 'git'}, {'status': 'affected', 'version': '3.0.0', 'lessThan': 'a7875e876a647572dd4c45da881b875092caac3d', 'versionType': 'git'}], 'defaultStatus': 'affected'}] Changed Description Simple Machines Forum 2.1 prior to 2.1.8 and 3.0 prior to 3.0 Alpha 5 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. 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. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 14, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-39903', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-14T01:56:17.608329Z'} -
New CVE Received by [email protected]
Jul. 10, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/SimpleMachines/SMF', 'vendor': 'SimpleMachines', 'product': 'SMF', 'versions': [{'status': 'affected', 'version': '2.1.0', 'lessThan': '2.1.8', 'versionType': 'semver'}, {'status': 'affected', 'version': '3.0.0', 'lessThan': '3.0.0 Alpha 5', 'versionType': 'custom'}], 'defaultStatus': 'affected'}] Added Description Simple Machines Forum 2.1 prior to 2.1.8 and 3.0 prior to 3.0 Alpha 5 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L Added CWE CWE-863 Added Reference https://github.com/SimpleMachines/SMF/commit/7d048f8d66aab9af51cd6ee110fbad103cf673e8 Added Reference https://github.com/SimpleMachines/SMF/commit/a7875e876a647572dd4c45da881b875092caac3d Added Reference https://github.com/SimpleMachines/SMF/pull/9181 Added Reference https://github.com/SimpleMachines/SMF/pull/9182 Added Reference https://www.vulncheck.com/advisories/simple-machines-forum-authorization-bypass-via-attachmentapprove-php