Auth bypass in Mybb

CVE-2026-45124

MyBB is free and open source forum software. Prior to 1.8.40, the Mod CP Report Center does not check permissions consistently, allowing moderators without report-management permission to mark reports as resolved. The modcp.php?action=do_reports Mark Selected as Read handler is reachable with canmodcp even without canmanagereportedcontent or canmanagereportedposts. When no forums are in scope, $flist_reports is empty and the UPDATE mybb_reportedcontent query executes without the expected permission-based limitation. This issue is fixed in version 1.8.40.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (24.7th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 24.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-45124: held from 0.002 to 0.003.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001

Affected products

  • Mybb — versions < 1.8.40

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-45124?
CVE-2026-45124 is a medium-severity vulnerability in Mybb, classified under Missing Authorization. CVSS score: 4.3/10. Published 2026-08-18.
How severe is CVE-2026-45124?
Medium severity. CVSS v3 base score is 4.3 out of 10.