Executive brief
Kimai, an open-source time-tracking application, contains a flaw where team leads can bypass intended restrictions to manage users and activities outside their authorized scope. By using specific backend programming interfaces, a team lead can add unauthorized users or business activities to their team, even if those items are hidden in the standard user interface. This could lead to unauthorized access to sensitive project data, incorrect reporting, and a breakdown of the security boundaries between different teams.
Technical details
An improper authorization vulnerability exists in Kimai's Team Controller API. While the frontend correctly restricts visible users and activities based on a Teamlead's scope, the backend endpoints `POST /api/teams/{id}/members/{userId}` and `POST /api/teams/{id}/activities/{activityId}` only verify if the caller has 'edit' permissions for the team. They fail to validate if the referenced User or Activity objects are within the caller's management domain. An authenticated attacker with Teamlead privileges can exploit this to attach arbitrary users or activities to their team. This can lead to privilege escalation as downstream authorization logic often trusts these team-object relationships for access control decisions. The issue is fixed in version 2.58.0 by adding explicit permission checks for the referenced entities.
Affected products
- Kimai kimai/kimai <= 2.57.0
Timeline
- 2026-06-11: disclosed
- 2026-07-14: advisory: GitHub Advisory published
- 2026-07-14: patched: Version 2.58.0 released