Attachment moderation bypass via assignment in permission check
Published Jul 10, 2026 · Updated Jul 10, 2026
Authorization bypass in Simple Machines Forum 2.1 before 2.1.8 and 3.0 before 3.0 Alpha 5 allows remote authenticated users to control attachments. AttachmentApprove::execute assigns [0] to allowed_boards instead of comparing it, so the truthy assignment bypasses the per-board approve_posts test. Any authenticated low-privileged account can approve, reject, enumerate, or delete pending attachments on any board, including other users' uploads.
Summary
What happened
Authorization bypass in Simple Machines Forum 2.1 before 2.1.8 and 3.0 before 3.0 Alpha 5 allows remote authenticated users to control attachments. AttachmentApprove::execute assigns [0] to allowed_boards instead of comparing it, so the truthy assignment bypasses the per-board approve_posts test. Any authenticated low-privileged account can approve, reject, enumerate, or delete pending attachments on any board, including other users' uploads.
The record
- CVE
- CVE-2026-39903
- Published
- Jul 10, 2026
- Updated
- Jul 10, 2026
- Vendor
- Simple Machines
- Product
- Simple Machines Forum
- Classifications
- CWE-863, T1565.001
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 10, 2026CVE publishedPublication date reported by the CVE source.
- Jul 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.1.0 <2.1.8
- Affected versionversion=3.0.0 <3.0.0 Alpha 5
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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