LOW 3.5 NVD
CVE-2026-45127
MyBB is free and open source forum software. Prior to 1.8.40, the ACP Mass Mail module does not validate certain requests correctly, allowing same-site attacker
MyBB is free and open source forum software. Prior to 1.8.40, the ACP Mass Mail module does not validate certain requests correctly, allowing same-site attackers to create draft entries from archived entries by embedding a specially crafted URL. The Resend route in Admin CP, Users & Groups, Mass Mail, Mass Mailing Archive duplicates archived mailing entries into new drafts with mybb_massemails.status set to 0 on GET requests without request forgery protection. The uniquely identifying implementation details include Users & Groups → Mass Mail → Mass Mailing Archive, mybb_massemails.status = 0, and admin/modules/user/mass_mail.php. This issue is fixed in version 1.8.40.
References
- https://github.com/mybb/mybb/commit/a95c5d6730b943adab7e54bc209c051f98843a3b
- https://github.com/mybb/mybb/releases/tag/mybb_1840
- https://github.com/mybb/mybb/security/advisories/GHSA-xx78-g79m-qvgq
- https://mybb.com/versions/1.8.40
This low severity vulnerability with a CVSS score of 3.5 was published on 2026-08-18 via NVD.
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