PHP CVE-2026-34390

Insufficient access control checks in _ProjectUsersAddCommand_ (used in *manage_proj_user_add.php* and REST API endpoint PUT /project/{id}/users) allows users having *manage_project_threshold* access level (*manager* by default) to grant project-level *administrator* access to any user (including themselves) in any Project they have *manager* rights in.

The normal project-user add form does restrict the selectable access levels to the actor's own project role or below. However, the backend handler still accepts a forged higher access_level value and writes it.

Impact

Privilege escalation.

The consequences of the privilege escalation are not as bad as it may sound, because having *administrator* access at Project level is effectively not very different from being *manager*, it does not actually give administrator privileges on the whole MantisBT instance. In particular, it does not let the upgraded user delete the Project or grant them any access to global administrative functions such as managing Users, Projects, Plugins, Custom Fields, etc.

Patches

• 69e0180f180ed5acf48a8d281a73683a7bf32461

Workarounds

None

Credits

Thanks to the following security researchers for independently discovering and responsibly reporting the issue:

• Dracosec Research Limited (Siu Nam Tang, Chris Chan, Krecendo Hui, William Lam)
• Vishal Shukla