Kimai: Improper Authorization in Project, Customer, and Activity Rate Edit Endpoints Allows Cross-Scope Rate Manipulation

Summary

Kimai 2.56.0 contains an authenticated improper authorization vulnerability in the Web rate editing flows for projects, customers, and activities. A user who can edit one authorized parent object can combine that authorized parent ID with the rate ID of a different, unauthorized parent object and thereby modify the unauthorized rate record.

This affects ProjectRate, CustomerRate, and ActivityRate editing. The issue is caused by missing parent-child consistency validation and allows cross-project, cross-customer, or cross-activity tampering of billing-related configuration.

Details

The issue affects the following Web routes:

• GET/POST /en/admin/project/{id}/rate/{rate}
• GET/POST /en/admin/customer/{id}/rate/{rate}
• GET/POST /en/admin/activity/{id}/rate/{rate}

In both cases, the parent object and the rate object are resolved independently from user-controlled route parameters. The controller only checks whether the current user may edit the parent object referenced by {id}, but it does not verify that the child rate object referenced by {rate} actually belongs to that same parent.

In these controllers, there is no validation such as:

• $rate->getProject() === $project
• $rate->getCustomer() === $customer
• $rate->getActivity() === $activity

This missing binding check is especially notable because the API delete endpoints already enforce the expected parent-child relationship.

This shows that parent-child consistency is already a recognized invariant in the application design, but the Web edit endpoints fail to enforce it for projects, customers, and activities.

A PoC was provided, but removed for security reasons.

Impact

This vulnerability allows authenticated users to tamper with billing-related rate configuration outside their authorized project, customer, or activity scope. An attacker can modify rate values belonging to other teams or business domains, which can affect time-based settlement, inherited pricing, cost calculations, budget reporting, revenue reporting, and downstream invoice generation.

Because the issue directly persists changes into kimai2_projects_rates, kimai2_customers_rates, and kimai2_activities_rates, it is a real cross-scope integrity vulnerability rather than a UI-only flaw. The attack breaks team-based isolation boundaries for high-value financial configuration.

Solution

The rate edit forms for customers, projects and activities now verify that the rate belongs to the parent referenced in the URL and reject the request otherwise.

See https://www.kimai.org/en/security/ghsa-2xgg-2x8h-8xw4 for more information.