Is CVE-2026-45127 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-45127?

CVE-2026-45127 has a CVSS v3 severity of LOW (3.5).

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CVE-2026-45127

Description

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.