Unrated

Kimai Timesheet API authorization bypass allows cross-team project reassignment

IdentifiersCVE-2026-52820CWE-863

CVE-2026-52820 is an authorization flaw in Kimai affecting the Timesheet API PATCH and POST endpoints. An authenticated user who is permitted to edit their own timesheets can exploit a query-builder logic issue involving an OR-bypass to assign their own timesheet entries to projects outside their authorized team scope. The vulnerable behavior fails to properly enforce team-based access controls when project associations are modified, allowing unauthorized reassignment of timesheets and disclosure of restricted project-related metadata in API responses. The issue was addressed by changing FormTrait so that project data is only forwarded for new timesheets and by adding a TimesheetTeamAccessValidator to validate team access when project or activity values change.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows an authenticated user to bypass intended team ACL restrictions and reassign their own timesheet records to arbitrary projects in the database. This can corrupt business data by polluting budgets, billing exports, and reporting workflows. It also exposes otherwise restricted project and customer metadata, including attributes such as names, currency, dates, and hierarchical relationships, through the API response path.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, restrict access to the Timesheet API endpoints to only highly trusted users, reduce or remove permissions that allow users to edit their own timesheets where operationally feasible, and monitor for anomalous timesheet updates involving unexpected project changes across team boundaries. Additional compensating controls should focus on enforcing server-side validation of project-to-team authorization before accepting timesheet modifications.

Remediation

Patch, then assume compromise.

Upgrade Kimai to version 2.57.0 or later. The vendor fix restricts project forwarding behavior in FormTrait for new timesheets only and introduces TimesheetTeamAccessValidator checks to enforce team authorization whenever project or activity assignments are changed.

PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

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VendorProductType

KimaiKimaiapplication

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ACTIVITY FEED

Recent activity

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0 SOURCESView more in app

No public activity observed for this vulnerability.

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Threat actor evidence

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Associated malware

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Detection signatures

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