CSRF in Mybb
CVE-2026-45119
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.
Vulnerability class: CSRF (Cross-Site Request Forgery)
CVSS v3 metric
CVSS v3 base score 4.6 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L.
Affected products
- Mybb — versions < 1.8.40
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-45119?
- CVE-2026-45119 is a medium-severity vulnerability in Mybb, classified under Cross-Site Request Forgery (CSRF). CVSS score: 4.6/10. Published 2026-08-18.
- How severe is CVE-2026-45119?
- Medium severity. CVSS v3 base score is 4.6 out of 10.