In June 2024, a critical security vulnerability was disclosed in the CyberArk Privileged Access Security (PAS) Solution, tracked as CVE-2024-42340. This vulnerability is rooted in CWE-602: Client-Side Enforcement of Server-Side Security. If exploited, it could let attackers bypass important security controls and access privileged actions by tampering with client-side code. In this deep dive, we’ll unpack what happened, show simple exploit examples, and guide you on how to stay safe.

What is CVE-2024-42340?

CyberArk is a leader in privileged access management (PAM). Their products are often the last line of defense before highly sensitive credentials. CVE-2024-42340 highlights a misstep where CyberArk’s web UI relies too much on the front-end (browser/client-side) to enforce permissions and security controls, instead of double-checking everything server-side.

The Vulnerability in a Nutshell:
Critical operations (like viewing secrets or approving requests) are hidden or disabled in the browser with JavaScript, but the server itself does not verify if the user has permission. So, a malicious user could simply re-enable those UI elements, or directly craft API calls, and the server might process them—even without real privileges.

CWE-602: Why Client-Side Enforcement is Bad

CWE-602 (MITRE link) is all about not trusting the client. The big risk is: attackers can always view, edit, and replay the client-side code, so anything enforced there (without backend checks) is security theater.

Get a lower-privilege account on CyberArk.

2. Inspect the Web App - See that some menu items/buttons are disabled or hidden via JavaScript.

Re-enable Features in the Browser

By using browser DevTools (F12), attackers can remove "disabled" attributes from buttons, or show hidden menu entries.

Interact with the API Directly

By monitoring network traffic (XHR/WebSocket), attackers notice what API endpoints the UI calls. They can then craft these API calls themselves, even if the UI prevents them through JavaScript.

Code Example: Re-enabling a Hidden Feature

Let’s say in the CyberArk web UI, the button to "View Secret" is only meant for admins. Their UI disables it like this:

<!-- Simplified HTML -->
<button id="view-secret-btn" disabled>View Secret</button>

With JavaScript, an attacker types in the browser console

// Remove the 'disabled' attribute
document.getElementById("view-secret-btn").disabled = false;

Now the attacker can click it. If the server doesn’t double-check on request, the action goes through!

Or, the “View Secret” action is disabled in the UI, but the API endpoint is

POST /api/vault/viewsecret
{
    "secretId": "123456",
    "userToken": "attacker's token"
}

Using curl or Postman

curl -X POST https://cyberark.example.com/api/vault/viewsecret \
  -H 'Authorization: Bearer <attacker_token>' \
  -d '{"secretId":"123456"}'

If the server does not check if the token’s user actually has the right role, the attacker gets the secret!

Audit Trail Bypass: Malicious actions are invisible if flaws in logging.

Imagine this flaw in a financial environment or a government system—devastating.

Patch: CyberArk has released updates. See original advisories:

- CyberArk Security Advisory
- NIST NVD Entry

Conclusion

CVE-2024-42340 is a powerful reminder: never trust the client! If your web app hides or disables “dangerous” features in JavaScript, but the backend naively trusts users, you’re at extreme risk. The CyberArk bug is a textbook CWE-602—simple for attackers to exploit, devastating for defenders.

Learn more:
- CyberArk Advisory
- CWE-602 Explanation

Pro tip: Always double-check that your backend enforces all access controls, even if your UI looks locked down.

If you’re a CyberArk user, patch now—and audit your web apps to avoid being the next CVE-2024-42340!

Timeline

Published on: 08/25/2024 08:15:03 UTC
Last modified on: 08/30/2024 19:47:36 UTC