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.