Kimai: Login CSRF in Default Team Creation Endpoints Allows Unauthorized Team and Permission Structure Changes

Summary

Kimai 2.56.0 contains authenticated cross-site request forgery issues in its default team creation shortcuts for projects, customers, and activities. These endpoints are exposed through GET routes and directly create or reuse a Team, add the current user as teamlead, and bind the target object to that team.

As a result, an attacker can trick a logged-in user with the required permissions into visiting a malicious page and cause unauthorized changes to team, teamlead, and object-binding relationships. This is a real authorization-structure modification issue rather than a harmless UI shortcut.

Details

The issue affects at least the following routes:

• GET /en/admin/project/{id}/create_team
• GET /en/admin/customer/{id}/create_team
• GET /en/admin/activity/{id}/create_team

Each of these routes is a GET endpoint, yet each performs persistent writes that alter authorization structure:

• create or reuse a Team
• add the current user as teamlead
• bind the target Project, Customer, or Activity to that team

A PoC was provided, but removed for security reasons.

Impact

This vulnerability allows an attacker to remotely alter permission topology while the victim is logged in. A successful exploit can create or reuse a team, assign the victim as its teamlead, and bind a project, customer, or activity to that team without intentional user action.

The pre-requisite is, that the logged-in user already has access to manage permissions of the object in question.

Because these routes modify authorization structure rather than a simple personal preference, the business impact can extend into visibility rules, assignment scope, team-based access control, reporting, and later privilege-expansion chains. This makes the issue materially more serious than a low-value cosmetic CSRF.