CVE-2026-84804 in Kimai
Summary
by MITRE • 09/02/2026
Kimai before 2.65.0 fails to properly validate permissions when removing team access to activities, projects, and customers via API endpoints. Authenticated users with edit_team permission can revoke team access without the required permissions_activity check, bypassing authorization controls.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in Kimai versions prior to 2.65.0 represents a critical failure in server-side access control logic within its RESTful API implementation. This flaw specifically affects the mechanisms used to manage team-based resource assignments for activities, projects, and customers. In secure web applications, particularly those handling sensitive business data like time tracking and project management systems, it is imperative that every action performed by an authenticated user undergoes a rigorous verification of their specific privileges relative to the target resource. The architecture of Kimai relies on distinct permission scopes to ensure that users can only modify resources they are explicitly authorized to manage. However, in this instance, the API endpoints responsible for revoking team access from these entities fail to enforce the necessary authorization checks before executing the deletion or modification operation.
The technical root cause lies in a missing validation step within the backend logic handling requests to remove team associations. While the application correctly verifies that the user possesses general edit_team permissions, it neglects to perform a secondary check for permissions_activity and related resource-specific rights. This oversight allows an authenticated attacker who holds only the edit_team permission level to bypass higher-level security controls. By crafting specific API calls targeting activities, projects, or customers, the attacker can strip team access from these resources without possessing the direct authority to manage them individually. This constitutes a classic Broken Access Control vulnerability where the principle of least privilege is violated due to insufficient granularity in permission verification during state-changing operations.
From an operational perspective, this flaw enables unauthorized modification of organizational structures and resource allocations within the Kimai environment. An attacker leveraging this weakness can disrupt team workflows by removing access rights from critical projects or activities, potentially leading to data isolation issues where legitimate users lose visibility into their assigned tasks. Furthermore, if these resources contain sensitive billing information or proprietary project details, the ability to alter access permissions could indirectly facilitate unauthorized exposure of data depending on how downstream systems interpret the changed state. The impact extends beyond simple configuration changes; it undermines the integrity of the role-based access control model that Kimai employs, allowing lower-privileged users to exert influence over high-value assets they should not be able to touch.
This vulnerability aligns with CWE-269, which describes Improper Privilege Assignment, as well as CWE-862, Missing Authorization, because the system fails to enforce required security policies during execution. In terms of offensive cybersecurity frameworks, this behavior is characteristic of ATT&CK technique T1078, Valid Accounts, specifically when combined with lateral movement or privilege escalation tactics where an attacker uses legitimate credentials to perform actions outside their intended scope. The exploitation does not require complex injection techniques but rather a straightforward misuse of existing API endpoints by leveraging the gap in permission validation logic.
To mitigate this risk, organizations running Kimai must immediately upgrade to version 2.65.0 or later, where these authorization checks have been corrected to ensure that revoking team access requires appropriate permissions for both the team and the specific resource being modified. Until an update is applied, administrators should restrict API access to only those users who absolutely require it and monitor logs for unusual patterns of permission changes initiated by accounts with limited edit_team privileges but no activity or project management rights. Implementing strict input validation on the server side and conducting regular security audits of role definitions can further reduce the attack surface associated with such logic flaws in enterprise time-tracking software.