Medium 4.6Published Aug 18, 2026

CVE-2026-45119MyBB: ACP UTF-8 Conversion CSRF

Updated under an hour ago (2026-10-19 07:00 UTC)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

MyBB is free and open source forum software. Prior to 1.8.40, the Admin CP UTF-8 Conversion module does not validate certain requests correctly, allowing same-site attackers to alter table encoding and deny service with a specially crafted URL. The do=all control flow in admin/modules/tools/system_health.php performs ALTER TABLE operations, column rewrite phases, and fulltext index rebuilds on GET requests for the database table named by the table parameter without request verification. The uniquely identifying implementation details include GET requests without request verification. This issue is fixed in version 1.8.40.

CVSS: 4.6 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L
Weakness (CWE): CWE-352
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Aug 19, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

mybb mybb mybb:mybb (from the name)	before 1.8.40	CNA record

References

https://github.com/mybb/mybb/security/advisories/GHSA-p48q-4vgf-q7x8x-refsource-confirm
https://github.com/mybb/mybb/commit/70d445d14c8350cc014be66f7874611abef70ab4x-refsource-misc
https://github.com/mybb/mybb/releases/tag/mybb_1840x-refsource-misc
https://mybb.com/versions/1.8.40x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.