Kimai: Timesheet PATCH/POST allows assigning to project outside user's team via query_builder OR-bypass

Summary

The Timesheet API PATCH /api/timesheets/{id} and POST /api/timesheets endpoints accept a user-supplied project ID and resolve it through a Symfony EntityType whose query_builder allows the submitted ID to satisfy the access predicate via an unconditional OR branch. As a result, any authenticated user can re-assign their own timesheet to any project in the database — including projects that belong to teams or customers they have no membership in and cannot otherwise see. The user can then read serialized project/customer details via GET /api/timesheets/{id}?full=true, leaking metadata (name, currency, customer hierarchy) that would otherwise be filtered out by the team ACL.

Details

Entry point — only ownership is checked in src/API/TimesheetController.php:317-355

#[IsGranted('edit', 'timesheet')]
#[Route(methods: ['PATCH'], path: '/{id}', name: 'patch_timesheet', requirements: ['id' => '\d+'])]
public function patchAction(Request $request, Timesheet $timesheet): Response
{
    ...
    $form = $this->createForm(TimesheetApiEditForm::class, $timesheet, [...]);
    $form->setData($timesheet);
    $form->submit($request->request->all(), false);
    if (false === $form->isValid()) { ... }
    $this->service->saveTimesheet($timesheet);
    ...
}

src/Voter/TimesheetVoter.php:134-142:

if ($subject->getUser()?->getId() === $user->getId()) {
    return $this->permissionManager->hasRolePermission($user, $permission . '_own_timesheet');
}

if (!$this->permissionManager->checkTeamAccessTimesheet($subject, $user)) {
    return false;
}

For an own-timesheet, only edit_own_timesheet is required. The voter does not look at the new project being submitted; it only validates the existing record's ownership.

Form replays user-controlled project ID into the access query

src/Form/TimesheetEditForm.php:60-71:

$isNew = true;
if (isset($options['data']) && $options['data'] instanceof Timesheet) {
    ...
    if (null !== $entry->getId()) {
        $isNew = false;
    }
    ...
}
$this->addProject($builder, $isNew, $project, $customer);

src/Form/FormTrait.php:59-100:

$builder->addEventListener(
    FormEvents::PRE_SUBMIT,
    function (FormEvent $event) use ($builder, $project, $customer, $isNew, $options): void {
        $data = $event->getData();
        $customer = \array_key_exists('customer', $data) && $data['customer'] !== '' ? $data['customer'] : null;
        $project = \array_key_exists('project', $data) && $data['project'] !== '' ? $data['project'] : $project;

        $event->getForm()->add('project', ProjectType::class, array_merge($options, [
            'group_by' => null,
            'query_builder' => function (ProjectRepository $repo) use ($builder, $project, $customer, $isNew) {
                $project = \is_string($project) ? (int) $project : $project;
                ...
                if ($isNew && \is_int($project)) {
                    $project = $repo->find($project);
                    if ($project !== null) {
                        if (!$project->getCustomer()->isVisible()) { ... $project = null; }
                        elseif (!$project->isVisible())            { $project = null; }
                    }
                }
                ...
                $query = new ProjectFormTypeQuery($project, $customer);
                $query->setUser($builder->getOption('user'));
                $query->setWithCustomer(true);
                return $repo->getQueryBuilderForFormType($query);
            },
        ]));
    }
);

Two problems compound:

1. The visibility re-check on line 73 is gated on $isNew. For PATCH, $isNew = false, so the closure passes the attacker-supplied ID straight through.
2. Even when $isNew = true (POST), the re-check only validates isVisible() — it does not validate team membership.

The query-builder unconditionally accepts the submitted ID

src/Repository/ProjectRepository.php:150-208:

public function getQueryBuilderForFormType(ProjectFormTypeQuery $query): QueryBuilder
{
    ...
    $mainQuery = $qb->expr()->andX();
    $mainQuery->add($qb->expr()->eq('p.visible', ':visible'));
    $mainQuery->add($qb->expr()->eq('c.visible', ':customer_visible'));
    if (!$query->isIgnoreDate()) { ... }
    if ($query->hasCustomers()) { ... }

    $permissions = $this->getPermissionCriteria($qb, $query->getUser(), $query->getTeams());
    if ($permissions->count() > 0) {
        $mainQuery->add($permissions);
    }

    $outerQuery = $qb->expr()->orX();
    if ($query->hasProjects()) {
        $outerQuery->add($qb->expr()->in('p.id', ':project'));     // <-- unconditional
        $qb->setParameter('project', $query->getProjects());
    }
    ...
    $outerQuery->add($mainQuery);
    $qb->andWhere($outerQuery);
    return $qb;
}

The final WHERE clause is roughly:

WHERE (p.id IN (:project)) OR (p.visible AND c.visible AND <date> AND <team-ACL>)

Because :project is the submitted ID itself, the first branch matches unconditionally, completely bypassing the team-ACL applied by getPermissionCriteria. Symfony's EntityType happily resolves the foreign Project entity, the form passes validation, and the timesheet is persisted with the new project_id.

No downstream validation closes the gap

• TimesheetService::saveTimesheet → updateTimesheet (src/Timesheet/TimesheetService.php:154-177) is explicitly documented as not validating.
• TimesheetBasicValidator only validates begin/end and project/activity coherence.
• TimesheetDeactivatedValidator::validateActivityAndProject (src/Validator/Constraints/TimesheetDeactivatedValidator.php:36-42) returns early for non-running existing timesheets.
• No validator anywhere in the timesheet pipeline checks that the project's team membership intersects the acting user's teams.

A PoC was provided, but removed for security reasons.

Impact

• Integrity: any authenticated user can attribute their own tracked time to any project ID in the database — including projects belonging to teams/customers they cannot see. This pollutes per-project budgets, billing exports and reports for other teams. There is no in-app warning that records belonging to outsiders have been added.
• Confidentiality: by reading the timesheet back via ?full=true, the attacker obtains serialized project and customer details (name, currency, start/end dates, customer hierarchy) which would normally be filtered by the team ACL.
• Privilege model: the edit_own_timesheet permission is part of the default ROLE_USER, so the bypass is reachable by every regular user without any administrator action.

The blast radius is bounded by what an attacker can persist (their own timesheet rows) and what the ?full=true serializer exposes — there is no direct ability to modify other teams' existing data.

Solution

• The FormTrait was updated to only pass the project forward for new timesheets
• A new TimesheetTeamAccessValidatorwas added, which checks if project or activity were changed. If that is the case, the team access permission is checked first

Find out more at https://www.kimai.org/en/security/ghsa-vrr2-g9gh-c3jc