Flowise is a drag & drop user interface to build a customized large language model flow. Prior to version 3.1.2, POST /api/v1/node-custom-function lacks route-level authorization, allowing any authenticated user or API key to submit arbitrary JavaScript to the Custom JS Function node. When E2B_APIKEY is not configured — the common deployment case — Flowise executes this code inside a NodeVM sandbox. This sandbox can be escaped, allowing an attacker to reach the host process object and execute system commands via child_process. The result is authenticated remote code execution on the Flowise server host. This issue has been patched in version 3.1.2.

Affected: npm: flowise

### Summary

`POST /api/v1/node-custom-function` lacks route-level authorization, allowing any authenticated user or API key to submit arbitrary JavaScript to the `Custom JS Function` node.

When `E2B_APIKEY` is not configured — the common deployment case — Flowise executes this code inside a `NodeVM` sandbox. This sandbox can be escaped, allowing an attacker to reach the host `process` object and execute system commands via `child_process`.

The result is authenticated remote code execution on the Flowise server host. CVSS v3.1: `AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H` = **9.9 Critical**.

### Details

Two distinct security boundaries are violated.

**1. Missing route-level authorization**

`packages/server/src/routes/node-custom-functions/index.ts` registers the endpoint with no permission middleware:

```ts router.post('/', nodesRouter.executeCustomFunction) ```

Other sensitive routes in the same codebase use explicit permission gates:

```ts // packages/server/src/routes/chatflows/index.ts router.post( '/', checkAnyPermission('chatflows:create,chatflows:update,agentflows:create,agentflows:update'), chatflowsController.saveChatflow ) ```

Global `/api/v1` authentication still applies, so this is not unauthenticated — but any valid session or API key reaches the endpoint without further restriction.

**2. NodeVM sandbox escape**

The endpoint forwards `body.javascriptFunction` through the following chain:

``` POST /api/v1/node-custom-function → packages/server/src/c…

Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in Flowise ausnutzen, um Code auszuführen, Objekte anderer Benutzer zu übernehmen, Informationen offenzulegen und weitere, nicht näher genannte Auswirkungen zu erzielen.