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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.

PUBLISHED Reserved 2026-04-07 | Published 2026-07-10 | Updated 2026-07-14 | Assigner VulnCheck




HIGH: 7.1CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

HIGH: 7.1CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L

Problem types

Incorrect Authorization

Product status

Default status
affected

2.1.0 (semver)
affected

7d048f8d66aab9af51cd6ee110fbad103cf673e8 (git)
unaffected

3.0.0 (semver)
affected

a7875e876a647572dd4c45da881b875092caac3d (git)
unaffected

Credits

Elure (Marasescu Mihnea-Luca) finder

VulnCheck coordinator

References

github.com/SimpleMachines/SMF/pull/9182 (Pull Request (v2.1)) issue-tracking

github.com/SimpleMachines/SMF/pull/9181 (Pull Request (v3.0)) issue-tracking

github.com/...ommit/7d048f8d66aab9af51cd6ee110fbad103cf673e8 (Patch Commit (v2.1)) patch

github.com/...ommit/a7875e876a647572dd4c45da881b875092caac3d (Patch Commit (v3.0)) patch

www.vulncheck.com/...zation-bypass-via-attachmentapprove-php third-party-advisory

cve.org (CVE-2026-39903)

nvd.nist.gov (CVE-2026-39903)

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