CVE-2026-121561

Label Studio fails to apply organization filters when resolving storage URIs for tasks and projects in proxy_api.py endpoints. Attackers can access other tenants' cloud storage objects by creating a separate organization and supplying arbitrary file URIs to presign or stream bucket contents.

Label Studio through 1.23.0 fails to validate webhook URLs, allowing authenticated users to dispatch requests to internal services including RFC 1918 addresses and cloud metadata endpoints. Attackers can create webhooks targeting private networks and exfiltrate annotation data by enabling payload transmission in outbound requests.

Label Studio does not scope the annotation detail endpoint to the requesting user's organization. AnnotationAPI in label_studio/tasks/api.py declares queryset = Annotation.objects.all() and provides no get_queryset override, so the default lookup retrieves any annotation by primary key. The view's permission_required entries name annotations.view, annotations.change and annotations.delete, and label_studio/core/permissions.py registers every permission with rules.is_authenticated, so the check is satisfied by any logged-in account and no object-level organization test runs. The sibling task endpoint does constrain its queryset with project__organization set to the requester's active organization, which is the boundary this path omits. Annotation identifiers are sequential integers, so an authenticated user of one organization can enumerate identifiers to read, modify and delete annotations belonging to other organizations on the same instance. The same unscoped queryset appears on AnnotationConvertAPI in the same file.