What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 4.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-18 · updated 2026-09-08
• Weakness: CWE-352

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.

Affected products

• mybb: before 1.8.40

References

• https://github.com/mybb/mybb/commit/70d445d14c8350cc014be66f7874611abef70ab4
• https://github.com/mybb/mybb/releases/tag/mybb_1840
• https://github.com/mybb/mybb/security/advisories/GHSA-p48q-4vgf-q7x8
• https://mybb.com/versions/1.8.40

Get alerted when CVE-2026-45119 or the next vulnerability affects your stack