MyBB: ACP UTF-8 Conversion CSRF

Description

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.

Scores

EPSS (exploitation in 30 days)

0.17% · top 94% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.6.

Weakness

• CWE-352: Cross-Site Request Forgery (CSRF) (opens in a new tab)All about CWE-352 and its CVEs

Affected products

• mybb · mybb

  • affected < 1.8.40

References (4)

• https://github.com/mybb/mybb/security/advisories/GHSA-p48q-4vgf-q7x8 (opens in a new tab)x_refsource_CONFIRM
• https://github.com/mybb/mybb/commit/70d445d14c8350cc014be66f7874611abef70ab4 (opens in a new tab)x_refsource_MISC
• https://github.com/mybb/mybb/releases/tag/mybb_1840 (opens in a new tab)x_refsource_MISC
• https://mybb.com/versions/1.8.40 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-45119](https://trackcve.app/badge/CVE-2026-45119.svg)](https://trackcve.app/cve/CVE-2026-45119)

Record last updated 19 Aug 2026, 14:41 UTC.