If your factory floor runs on Mitsubishi Electric Corporation’s MELSEC iQ-F Series CPU modules, it’s time to pay attention. CVE-2023-7033 is a real-world Denial of Service (DoS) threat that doesn’t require fancy hacker skills—just an Internet connection and a classic network attack. Let’s unpack what’s going on, see how the exploit works, and what you can do about it.

What Is CVE-2023-7033?

CVE-2023-7033 is an _Insufficient Resource Pool_ vulnerability found in the Ethernet communication function of certain MELSEC iQ-F Series CPUs. In plain English, this means the device doesn’t do a good enough job managing how it handles incoming connections.

A remote attacker can send a bunch of fake connection requests (TCP SYN packets) and, as a result, lock up the device’s ability to communicate over the network for a certain period of time. While the CPU keeps running, Ethernet comms go down—potentially disrupting your manufacturing process.

Here’s the play-by-play

1. The Attacker Sends Many SYN Packets: The attacker floods the CPU’s Ethernet port with a huge number of initial connection requests (TCP SYNs), but never finishes the handshake.
2. Resource Pool Gets Exhausted: The CPU tries to keep track of all these half-open connections, but its table fills up.
3. New Connections Get Ignored: Once the table is full, the CPU stops responding to any new incoming network connections. You lose access—at least until existing half-open connections time out and the situation clears itself.

Proof-of-Concept: SYN Flood in Python

You don’t need cutting-edge exploit code. Here’s what an attacker might use, with Python and the classic scapy library.

from scapy.all import *

target_ip = "192.168.1.100"   # Replace with your MELSEC CPU's IP address
target_port = 800            # Use actual port in use (default: 800 for MELSEC CPUs)

for i in range(100):         # Adjust number for impact
    ip = IP(dst=target_ip)
    # Spoof random source ports
    tcp = TCP(sport=RandShort(), dport=target_port, flags="S")
    pkt = ip/tcp
    send(pkt, verbose=)

This script sends 1,000 SYN packets. With a few more lines of code and running it in loops, the disruption could last much longer.

WARNING: Don’t run this on a production network, or you could bring down real machines!

Exploit Details and Observations

- Target: MELSEC iQ-F Series CPU modules, including FX5U, FX5UC, FX5UJ, and similar, with Ethernet function.

Attack Vector: Ethernet (over LAN or potentially via remote access if exposed).

- Impact: Temporary loss of Ethernet communication (DoS); the CPU may still execute control logic, but remote monitoring, programming, or data transfer is disrupted.
- Duration: The denial lasts until the CPU’s half-open connection table is cleared, either by timeouts or a reset.

Official References

- Mitsubishi Electric Security Advisory (2024-01-12)
- NIST NVD CVE-2023-7033 Entry

Remediation and Mitigation

Unfortunately, this class of vulnerability is tough to patch in fielded hardware. Here’s what Mitsubishi recommends and what you can do:

- Network Segmentation: Make sure only trusted devices can talk to your MELSEC CPUs. Use VLANs or dedicated control networks.

Physical Security: Don’t expose control device networks to the Internet. Ever.

- Firmware Updates: Check frequently with Mitsubishi Electric for potential software updates or advisories:
MELSEC iQ-F Series Product Page
Mitsubishi Component Security Center

Final Thoughts

CVE-2023-7033 is a reminder that even industrial devices are vulnerable to old-school network attacks. Until better resource management makes it to production devices, your best defense is classic: keep the controllers on a locked-down network, and don’t let just anybody connect to them.

If you run Mitsubishi MELSEC iQ-F Series in your operation, review your network exposure today. As always, if you have to ask, “Are we exposed?”—it’s already too late.


Stay safe on the factory floor. If you need deep-dive help, consult your Mitsubishi support rep or a trusted OT security specialist.


*Exclusive post for security professionals and PLC operators. Reproduction not permitted without attribution.*

Timeline

Published on: 02/27/2024 04:15:06 UTC
Last modified on: 02/28/2024 01:15:07 UTC