CVE-2026-58054 PUBLISHED

MyBB - Privilege Escalation from Limited ACP User Management to Administrator

Assigner: VulnCheck
Reserved: 28.06.2026 Published: 28.06.2026 Updated: 28.06.2026

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.

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 7.2

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

CVSS 3.1

CVSS Vector: 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
CVSS Score: 8.6

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	None
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	High
User Interaction	None

CVSS 4.0

Product Status

Vendor	MyBB
Product	MyBB
Versions	Default: affected affected from 0 to 1.8.40 (incl.)

CVE-2026-58054 PUBLISHED

MyBB - Privilege Escalation from Limited ACP User Management to Administrator

Metrics

Product Status

Credits

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Problem Types