Flowise: RCE via NodeVM Sandbox Escape in executeJavaScriptCode() nodeVMOptions Override
Summary
A sandbox escape vulnerability in executeJavaScriptCode() allows any authenticated user to execute arbitrary system commands as root on the Flowise server. The function accepts caller-provided nodeVMOptions that override the
default sandbox security settings via JavaScript's spread operator, allowing an attacker to re-enable blocked modules like child_process and fs.
Details
The vulnerability is in packages/components/src/utils.ts at line 1755:
```typescript
const finalNodeVMOptions = { ...defaultNodeVMOptions, ...nodeVMOptions }
The executeJavaScriptCode() function (line 1569) creates a NodeVM sandbox with secure defaults that restrict which Node.js built-in modules can be required:
async (code, sandbox, options = {}) => {
const { nodeVMOptions = {} } = options;
// ...
const defaultNodeVMOptions = {
require: {
builtin: builtinDeps, // restricted allowlist — blocks child_process, fs, os, etc.
mock: secureWrappers
},
eval: false,
wasm: false
}
const finalNodeVMOptions = { ...defaultNodeVMOptions, ...nodeVMOptions } // ← VULN: caller overrides security settings
const vm = new NodeVM(finalNodeVMOptions)
}
```
The spread operator allows any caller to override require.builtin with ["*"], which permits all Node.js built-in modules including child_process.
Taint 01: Route Registration
packages/server/src/routes/node-custom-functions/index.ts (line 8)
Taint 02: Controller
executeCustomFunction() passes req.body to service — packages/server/src/controllers/nodes/index.ts (line 90)
Taint 03: Service
executeCustomNodeFunction() loads the customFunction node and calls init() with user-provided javascriptFunction — packages/server/src/utils/executeCustomNodeFunction.ts (line 49)
Taint 04: Sandbox Entry
Code runs inside NodeVM via executeJavaScriptCode() — packages/components/src/utils.ts (line 1760)
Taint 05: Escape
Inside the sandbox, the attacker requires flowise-components/dist/src/utils.js by absolute path (bypassing the module allowlist), obtaining a reference to executeJavaScriptCode() itself
Taint 06: Override
The attacker calls executeJavaScriptCode() with nodeVMOptions: { require: { builtin: ["*"] } }, which overrides the security defaults at line 1755: { ...defaultNodeVMOptions, ...nodeVMOptions }
