MyBB: ACP Mass Mail draft resend CSRF

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-45127
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-18 16:17:07 UTC
Updated2026-09-08 21:02:26 UTC
DescriptionMyBB 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.

Risk And Classification

Primary CVSS: v3.1 3.5 LOW from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

EPSS: 0.001320000 probability, percentile 0.030970000 (date 2026-09-08)

Problem Types: CWE-352 | CWE-352 CWE-352: Cross-Site Request Forgery (CSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.5LOWCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
3.1CNADECLARED3.5LOWCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mybb Mybb affected < 1.8.40 Not specified

References

ReferenceSourceLinkTags
github.com/mybb/mybb/releases/tag/mybb_1840 [email protected] github.com
mybb.com/versions/1.8.40 [email protected] mybb.com
github.com/mybb/mybb/security/advisories/GHSA-xx78-g79m-qvgq [email protected] github.com
github.com/mybb/mybb/commit/a95c5d6730b943adab7e54bc209c051f98843a3b [email protected] github.com
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