Vulnerability 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.
CVSS Score
LOW
Related Weaknesses (CWE)
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
FAQ
What is CVE-2026-45127?
CVE-2026-45127 is a vulnerability with a CVSS score of 3.5 (LOW). 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 ...
How severe is CVE-2026-45127?
CVE-2026-45127 has been rated LOW with a CVSS base score of 3.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-45127?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.