MyBB: ACP Mass Mail draft resend CSRF
Published Aug 18, 2026
3.5
LOWCVSS 3.1
EPSS 0.17%
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.
Affected products
-
- Version < 1.8.40StatusaffectedConstraints-
- Version
No data.
No data.
No Red Hat product state for this CVE.
No package ranges for this CVE.
Remediation
No remediation recorded yet.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
No CVSS v3.0 score for this CVE.
No CVSS v2.0 score for this CVE.
This CVE is not in the KEV list.
CISA SSVC (Vulnrichment)
Stakeholder-Specific Vulnerability Categorization from CISA ADP.
Exploitation
NoneAutomatable
NoTechnical Impact
PartialDecision
n/aAssessed Aug 19, 2026 · SSVC 2.0.3
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 3, 2026.
Score over time
Jun–Oct 2026- EPSS v4
- EPSS v5
Percentile over time
- EPSS v4
- EPSS v5
Table of values (3 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 3, 2026 | 0.17% (0.00173) | 6.14th | v5 (v2026.06.15) |
| Aug 19, 2026 | 0.13% (0.00132) | 3.23th | v5 (v2026.06.15) |
| Jun 12, 2026 | 0.01% (0.00011) | 1.44th | v4 (v2025.03.14) |
References (4)
- https://github.com/mybb/mybb/commit/a95c5d6730b943adab7e54bc209c051f98843a3b x_refsource_MISC
- https://github.com/mybb/mybb/releases/tag/mybb_1840 x_refsource_MISC
- https://github.com/mybb/mybb/security/advisories/GHSA-xx78-g79m-qvgq x_refsource_CONFIRM
- https://mybb.com/versions/1.8.40 x_refsource_MISC
| Link | Providers | Tags |
|---|---|---|
| https://github.com/mybb/mybb/commit/a95c5d6730b943adab7e54bc209c051f98843a3b | x_refsource_MISC | |
| https://github.com/mybb/mybb/releases/tag/mybb_1840 | x_refsource_MISC | |
| https://github.com/mybb/mybb/security/advisories/GHSA-xx78-g79m-qvgq | x_refsource_CONFIRM | |
| https://mybb.com/versions/1.8.40 | x_refsource_MISC |
Change history (0)
No recorded changes yet.