The Open Door Policy: Smashing IBM API Connect for Instant Admin Access

IBM API Connect is the heavy artillery of enterprise API management. It’s what large organizations use to expose their internal data and services to the world in a controlled manner. The Developer Portal is the storefront for this data—it's where third-party developers go to register apps, get API keys, and read documentation.

Because it’s a portal intended for external developers, it is almost always exposed to the public internet. It has to be. And that makes it a juicy target. If you compromise the portal, you don't just deface a website; you gain insight into the organization's entire API surface, access potentially sensitive documentation, and if you can escalate privileges, you might even be able to push malicious API configurations or steal active credentials.

CVE-2025-13915 is a critical authentication bypass (CWE-305) located specifically in the 'self-service sign-up' mechanism. This is the digital equivalent of a bank vault where the 'Open Account' form has a checkbox that says 'I am the Bank Manager' and the system actually believes you.

The vulnerability lies in the logic governing how new users are created when self-service sign-up is enabled. In a secure system, a user registration flow involves a state machine: Request -> Pending Verification -> Verified -> Active. The critical transition from Pending to Active (or the assignment of privileges) must be guarded by server-side logic that cannot be influenced by the client.

In CVE-2025-13915, this state machine is broken. The application appears to suffer from a logic flaw where input parameters provided during the initial sign-up request are implicitly trusted or improperly sanitized. This is a classic Mass Assignment or Parameter Pollution scenario combined with weak state validation.

When a user submits the registration form, the backend likely creates the user object based on the submitted JSON payload. If the backend fails to filter out privileged fields (like status, role, or is_verified) before persisting that object to the database, an attacker can simply inject these fields into their request. The system sees the "status": "active" in the payload, writes it to the database, and effectively bypasses the email verification or admin approval steps entirely.

While IBM hides their source code behind binary distributions and compiled PHP/Node modules (the Portal is often Drupal-based under the hood), we can reconstruct the vulnerability pattern based on the CWE and the attack vector.

The Vulnerable Pattern

Imagine a controller handling user registration that blindly accepts user input to hydrate a User object. This is a common sin in modern web frameworks.

// VULNERABLE LOGIC (Conceptual)
app.post('/api/user/register', async (req, res) => {
  const userInput = req.body;
 
  // DANGER: We are spreading the entire request body into the create method.
  // If the attacker sends {"username": "hacker", "role": "admin"}, we are doomed.
  const newUser = await User.create({
    ...userInput,
    created_at: new Date()
  });
 
  // The developer assumes 'role' defaults to 'dev' in the schema,
  // but the spread operator overrides it.
  
  if (newUser) {
    return res.json({ status: "success", token: generateToken(newUser) });
  }
});

The Secure Pattern

The fix involves strict input filtering (Allow-listing) and enforcing state transitions server-side, ignoring whatever status the client claims to have.

// SECURE LOGIC
app.post('/api/user/register', async (req, res) => {
  const userInput = req.body;
 
  // FIX: Explicitly extract only safe fields.
  const safePayload = {
    username: userInput.username,
    email: userInput.email,
    password: hash(userInput.password),
    // ENFORCE: Hardcode status and role. User input is ignored here.
    role: 'developer',
    status: 'pending_verification'
  };
 
  const newUser = await User.create(safePayload);
  
  // No token generation until verification logic runs separate from this flow.
  return res.json({ status: "pending_email_verification" });
});

The patch likely forces the self-service controller to ignore any privilege-related keys in the POST body, ensuring the account starts in a locked state regardless of what the attacker sends.

Exploiting this requires no special tools—just a web proxy like Burp Suite and a lack of moral compass. Since the vulnerability is in the self-service sign-up, the attack surface is the public registration page.

Attack Chain

1. Recon: Identify the IBM API Connect Developer Portal. Check if the "Create Account" or "Sign Up" button is visible (Self-Service enabled).
2. Capture: Fill out the registration form normally. Intercept the POST request before it leaves your browser.
3. Inject: Modify the JSON payload. We are looking to override default values.
   • Add: "status": 1 (or "active", true)
   • Add: "roles": ["admin"] or "group": "administrators"
   • Add: "email_verified": true
4. Send: Forward the manipulated request to the server.
5. Profit: If vulnerable, the server responds with a 200 OK and potentially an immediate session token. You are now logged in. If you injected the admin role, you now own the portal.

From here, an attacker can modify API definitions, revoke legitimate keys, or use the portal's CMS features to upload web shells if the CMS underlying the portal (often Drupal) is misconfigured.

Why is this a CVSS 9.8? Because it checks every box for a disaster scenario: Network Vector, Low Complexity, No Privileges, and High Impact.

By bypassing authentication at the registration phase, the attacker defeats the primary security boundary of the application. There is no need to phish credentials, brute force passwords, or find a session ID. The front door is effectively unlocked.

Consequences include:

• Data Exfiltration: Access to private API documentation and endpoints.
• Service Disruption: Deleting legitimate developer accounts or API keys, causing downstream outages for apps relying on those APIs.
• Reputation Damage: Hosting malware or phishing pages on a trusted domain (the Developer Portal).
• Lateral Movement: If the portal shares authentication mechanisms (LDAP/OIDC) with other IBM components, this could be a stepping stone into the deeper management network.

IBM has released Interim Fixes (iFixes) for versions 10.0.8.x and 10.0.11.0. Applying these binary patches is the only way to permanently close the hole while keeping functionality active.

Immediate Mitigation Strategy: If you cannot patch immediately (and let's be honest, enterprise patching windows are slow), you MUST disable self-service sign-up.

1. Log in to the Cloud Manager or API Manager UI.
2. Navigate to Settings > User Registry.
3. Uncheck "Allow self-service sign-up".

This moves the portal to an "Invite Only" model. It increases administrative overhead (someone has to manually approve or invite every dev), but it completely neutralizes the attack vector. It's a trade-off between convenience and not getting hacked. Choose wisely.