CVE-2026-39903: Incorrect Authorization in SimpleMachines SMF
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.
AI Analysis
Technical Summary
CVE-2026-39903 is an authorization bypass vulnerability in Simple Machines Forum (SMF) affecting versions 2.1.0 and 3.0.0 prior to specific commits. The issue arises from a single-character operator error in Sources/Actions/AttachmentApprove.php, causing the permission check to always succeed regardless of user privileges. Consequently, authenticated users with low privileges can perform actions reserved for users with approve_posts permission, including approving, rejecting, or deleting any pending attachments across boards. This flaw allows bypassing moderation controls and unauthorized enumeration and deletion of other users' attachments.
Potential Impact
The vulnerability allows authenticated low-privileged users to bypass intended authorization controls and perform moderation actions on attachments without proper permissions. This can lead to unauthorized approval, rejection, or deletion of attachments, potentially disrupting forum content moderation and integrity. It also enables enumeration and deletion of other users' pending attachments, which may impact user trust and forum operations.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch information is provided in the available data. Until a patch is released, administrators should monitor for updates from Simple Machines and consider restricting attachment-related permissions to trusted users only.
CVE-2026-39903: Incorrect Authorization in SimpleMachines SMF
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.
CVSS v4.0
Score 7.1high
Affected software
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-39903 is an authorization bypass vulnerability in Simple Machines Forum (SMF) affecting versions 2.1.0 and 3.0.0 prior to specific commits. The issue arises from a single-character operator error in Sources/Actions/AttachmentApprove.php, causing the permission check to always succeed regardless of user privileges. Consequently, authenticated users with low privileges can perform actions reserved for users with approve_posts permission, including approving, rejecting, or deleting any pending attachments across boards. This flaw allows bypassing moderation controls and unauthorized enumeration and deletion of other users' attachments.
Potential Impact
The vulnerability allows authenticated low-privileged users to bypass intended authorization controls and perform moderation actions on attachments without proper permissions. This can lead to unauthorized approval, rejection, or deletion of attachments, potentially disrupting forum content moderation and integrity. It also enables enumeration and deletion of other users' pending attachments, which may impact user trust and forum operations.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch information is provided in the available data. Until a patch is released, administrators should monitor for updates from Simple Machines and consider restricting attachment-related permissions to trusted users only.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-04-07T20:57:06.209Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a511ed468715ace43d6893c
Added to database: 07/10/2026, 16:33:24 UTC
Last enriched: 07/30/2026, 00:36:06 UTC
Last updated: 08/23/2026, 10:52:08 UTC
Views: 94
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.