GHSA-hp26-q66v-q2w7: Flowise: mass assignment breaks multi-tenant isolation

### Summary A Mass Assignment vulnerability exists in the assistant update endpoint of FlowiseAI. The endpoint allows authenticated users to modify server-controlled properties such as workspaceId, createdDate, and updatedDate when updating an assistant resource. Due to missing server-side validation and authorization checks, an attacker can manipulate the workspaceId field and reassign assistants to arbitrary workspaces. This breaks tenant isolation in multi-workspace environments. ### Details The endpoint responsible for updating assistants: **PUT /api/v1/assistants/{assistantId}** accepts a JSON request body containing assistant metadata. However, the server does not restrict which properties may be modified by the client. As a result, user-controlled request bodies can include additional fields that should normally be controlled only by the backend. Server-controlled fields that can be manipulated include: 1. workspaceId 2. createdDate 3. updatedDate These fields appear to be directly mapped to the underlying database entity without strict DTO whitelisting or authorization checks. For example, the following request body was accepted: ```json { "details": "", "credential": "11ca7fef-c9b1-4c87-aa54-e547aed8a249", "iconSrc": null, "type": "CUSTOM", "createdDate": "2026-03-06T17:31:04.000Z", "updatedDate": "2026-03-06T17:31:55.000Z", "workspaceId": "11111111-2222-3333-4444-555555555555" } ``` This indicates that internal, server-controlled properties can be modified by an authenticated user. ### PoC 1. Authenticate to the Flowise interface. 2. Capture the request used to update an assistant: ```http PUT /api/v1/assistants/<ASSISTANT_ID> Content-Type: application/json Modify the request body by injecting server-controlled fields: { "details": "", "credential": "11ca7fef-c9b1-4c87-aa54-e547aed8a249", "iconSrc": null, "type": "CUSTOM", "createdDate": "2026-03-06T17:31:04.000Z", "updatedDate": "2026-03-06T17:31:55.000Z", "workspaceId": "11111111-2222-3333-4444-555555555555" } ``` 3.Send the request. Observe that the response accepts and persists the attacker-controlled workspaceId and metadata fields. ### Impact This vulnerability allows authenticated users to manipulate internal attributes of assistant resources. Confirmed impacts include: - Cross-workspace reassignment of assistants (workspaceId) - Unauthorized modification of metadata (createdDate, updatedDate) In multi-tenant deployments, this may allow an attacker to move assistants between workspaces without authorization, breaking tenant isolation boundaries.

An attacker with a legitimate low-privilege account on a shared enterprise Flowise instance authenticates and creates a test assistant in their own workspace. Using an intercepting proxy, they capture the PUT /api/v1/assistants/{id} request and observe the accepted JSON schema. They then enumerate target workspace UUIDs—potentially discoverable from API error messages, URL patterns, or by observing UUIDs embedded in shared Flowise links—and replay the update request with an injected workspaceId pointing to a victim tenant's workspace. The server accepts and persists the manipulated field without validation. The attacker's assistant is now visible and operational within the victim workspace, and depending on the Flowise configuration, may inherit that workspace's connected LLM credentials, database connections, and tool integrations—enabling further lateral movement into the victim tenant's AI infrastructure without ever touching the victim's credentials.