What is CVE-2026-39903?

CVE-2026-39903 is a high-severity vulnerability in Simplemachines Smf, classified under Incorrect Authorization. CVSS score: 7.1/10. Published 2026-07-10.

How severe is CVE-2026-39903?

High severity. CVSS v3 base score is 7.1 out of 10.

Auth bypass in Simplemachines Smf

CVE-2026-39903

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 pas…

Vulnerability class: Broken Access Control

CVSS v3 metric

CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L.

Affected products

Simplemachines Smf — versions 2.1.0, 3.0.0

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

disclosure@vulncheck.com (issue-tracking)
disclosure@vulncheck.com (issue-tracking)
disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-39903?: CVE-2026-39903 is a high-severity vulnerability in Simplemachines Smf, classified under Incorrect Authorization. CVSS score: 7.1/10. Published 2026-07-10.
How severe is CVE-2026-39903?: High severity. CVSS v3 base score is 7.1 out of 10.