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Improper Privilege ManagementWeakness · CWE-269

CVE-2026-58054

HIGH · 7.2 CVSS v3.1 Published 2026-06-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
78/100
Remediation priority · High
Remotely reachable Zero-click 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

MyBB 1.8.40's admin control panel user module allows a limited admin (with only user-management permissions) to assign any usergroup, including the privileged Administrators group (gid=4). The verify_usergroup() function in the user datahandler unconditionally returns true without checking if the assigning admin has permission to grant elevated privileges, enabling privilege escalation.

MitigationImplement authorization checks in verify_usergroup() to validate the admin's permissions before allowing assignment of privileged usergroups, and restrict the usergroup dropdown options presented to limited admins.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm MyBB version is 1.8.40
    Check the admin control panel version under Admin CP > Home > Dashboard, or inspect the version.php file in the MyBB root directory for the $mybbversion variable
    Affected if The installed version is 1.8.40 specifically (the only version listed as affected)
  2. Verify limited admin accounts exist with user-management permissions
    In Admin CP, go to Users & Groups > Admins and review admin accounts. Identify any admin that has only user-management related permissions without full administrative access
    Affected if There exists at least one admin account with limited permissions focused on user management
  3. Inspect the verify_usergroup function in the user datahandler
    Locate the file inc/datahandlers/user.php (or similar path depending on installation) and examine the verify_usergroup() function. Check if it performs authorization validation before allowing privileged usergroup assignments
    Affected if The verify_usergroup() function returns true unconditionally without checking if the assigning admin has permission to grant elevated privileges such as gid=4 (Administrators group)
  4. Check for presence of privileged usergroups
    In Admin CP, go to Users & Groups > Groups and verify the existence of the Administrators group (typically gid=4). Also check for other privileged groups that should only be assignable by super admins
    Affected if Privileged usergroups including the Administrators group (gid=4) exist in the system and could be assigned

A user is affected if running MyBB 1.8.40 with the verify_usergroup() function lacking authorization checks, allowing limited admins to escalate privileges by assigning the Administrators group.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement authorization checks in verify_usergroup() to validate the admin's permissions before allowing assignment of privileged usergroups, and restrict the usergroup dropdown options presented to limited admins.

Recommended fix Moderate confidence

MyBB 1.8.41 or later (the next stable release containing the verify_usergroup() fix)

  1. 1. Identify the current MyBB installation version by checking the admin dashboard or version file.
  2. 2. Navigate to the MyBB download repository (download.mybb.com) to obtain the latest stable release.
  3. 3. Before upgrading, perform a complete backup of the database and all files.
  4. 4. Upload the new version files, overwriting the existing installation.
  5. 5. Run the upgrade script through the browser (usually by accessing install/upgrade.php).
  6. 6. Verify the fix by logging in as a limited admin with user-management permissions and confirming they cannot assign the Administrators usergroup (gid 4).
Caveat Standard MyBB upgrade risks apply: ensure plugins are compatible with the new version and test thoroughly in a staging environment before production deployment.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-58054 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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