CVE-2026-58054 | MyBB 1.8.40 does not restrict which usergroup a limited Admi… | CVSS 7.2 HIGH

Description

MyBB 1.8.40 does not restrict which usergroup a limited Admin Control Panel user may assign when creating or editing users; the user module offers the Administrators group (gid 4) and its datahandler's verify_usergroup() unconditionally returns true. An admin holding only the delegated user-management permission can assign the Administrators group to an account and escalate to the full Administrator permission set.

Metadata

CVE ID: CVE-2026-58054
State: PUBLISHED
Assigner: VulnCheck
Reserved: 2026-06-28 00:55 UTC
Published: 2026-06-28 01:32 UTC
Last updated: 2026-06-28 01:32 UTC
Primary CWE: CWE-269
Improper Privilege Management
Vendor / Product: MyBB / MyBB
Sources: cve.org · NVD

Severity & Metrics

7.2 HIGH CVSS 3.1

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

Affected products (1)

Vendor	Product	Platform	Versions
MyBB	MyBB	—	0 ≤ 1.8.40

Weakness (CWE)

CWE	Source	Description
CWE-269	cna	Improper Privilege Management

CVSS scores (2)

Score	Severity	Version	Source	Vector
8.6	HIGH	4.0	cna	CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
7.2	HIGH	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

References (2)

Proof of Concept https://github.com/bikini/exploitarium/tree/main/mybb-limited-acp-to-admin
VulnCheck Advisory: MyBB - Privilege Escalation from Limited ACP User Management to Administrator https://www.vulncheck.com/advisories/mybb-privilege-escalation-from-limited-acp-user-management-to-administrator