When it comes to industrial control systems (ICS), reliability and stability are of the utmost importance. But sometimes, hidden weaknesses in software can cause unexpected and disruptive results. One such flaw is CVE-2022-0222, a critical weakness discovered in certain Schneider Electric Modicon M340 automation products. In this article, we’ll break down what this vulnerability is, why it’s dangerous, how it works, and what you can do about it — using simple, practical explanations and real-world code examples.

What is CVE-2022-0222?

In plain terms, CVE-2022-0222 exposes a security hole in some Schneider Electric Modicon M340 controllers and their Ethernet communication modules. The technical problem is called CWE-269: Improper Privilege Management. This means the software doesn’t manage permissions or access as it should, which can result in unauthorized actions.

The specific danger of this flaw: Just by sending a crafted SNMP (Simple Network Management Protocol) request to the affected device, an attacker can cause the controller’s Ethernet communication to shut down. This means the device won’t be able to talk to other systems—potentially knocking out industrial operations.

This is a classic denial of service (DoS) attack: the controller won’t respond, so your automated processes could grind to a halt.

BMXNOR\* versions prior to v1.7 IR24

A full list of affected part numbers is available in Schneider’s official advisory (SEVD-2022-011-01).

What is SNMP, and Why is it a Problem Here?

SNMP is a protocol used to manage network devices—computers, switches, routers, and industrial controllers. Normally, engineers use SNMP to monitor device status or configure devices remotely.

But in this case, the affected Modicon units don’t properly check if an incoming SNMP request should be allowed to do certain things (improper privilege management). When the wrong kind of request is received—specifically crafted to exploit this bug—it causes the module to hang or shut down communications entirely.

How Does the Exploit Work?

While the exact technical details about the exploit’s payload are often not disclosed to prevent widespread abuse, public advisories and proof-of-concept examples do exist showing how an attacker would take advantage.

Send a specially crafted SNMP request.

By connecting to the SNMP service on the device (usually UDP port 161), an attacker sends malformed or otherwise “illegal” requests, exploiting the privilege management flaw.

Ethernet communication is disrupted.

The module’s network stack crashes, and it will stop responding to SCADA, programming stations, or HMI systems until it is manually reset or re-powered.

Example: How This Can Be Exploited (A Code Snippet)

Below is a Python example using the popular pysnmp library, showing how one might send an SNMP request to a vulnerable device. This is for demonstration and defensive testing only. Do not attack systems you don’t own!

from pysnmp.hlapi import *

# Details for the device
target_ip = '192.168..100'  # Replace with Modicon unit’s IP
comm_string = 'public'  # Community string
bad_oid = '1.3.6.1.4.1.12345.1.1.1.9999'  # Nonexistent or 'crafted' OID

errorIndication, errorStatus, errorIndex, varBinds = next(
    getCmd(SnmpEngine(),
           CommunityData(comm_string, mpModel=),  # SNMPv1, often used
           UdpTransportTarget((target_ip, 161), timeout=1, retries=),
           ContextData(),
           ObjectType(ObjectIdentity(bad_oid)))
)

if errorIndication:
    print(f'Error detected: {errorIndication}')
elif errorStatus:
    print(f'SNMP error: {errorStatus.prettyPrint()}')
else:
    print('Request sent. Check if device is still reachable.')

*Note: The specific OID and payload required to crash the device may differ (Schneider and security researchers do not publish the exact one). The above is illustrative, showing that sending arbitrary or unexpected SNMP requests can trigger the vulnerability.*

Loss of Communication:

All Ethernet communication to the controller is cut off—potentially including critical automation functions.

See official update bulletin:

SEVD-2022-011-01

Disable SNMP if Not Needed

If you don’t use SNMP for network management, turn it off via the device’s configuration or firewall.

Network Segmentation

Never expose industrial controllers to public or untrusted networks. Isolate them in private/VLAN’d subnets, with firewalls blocking SNMP except from management workstations.

Change Default Community Strings

Don’t use “public” or “private” as your SNMP community string—they’re widely known and targeted.

Schneider Electric advisory (SEVD-2022-011-01):

https://www.se.com/ww/en/download/document/SEVD-2022-011-01/

CVE Record:

https://nvd.nist.gov/vuln/detail/CVE-2022-0222

CWE-269 Details:

https://cwe.mitre.org/data/definitions/269.html

Conclusion

CVE-2022-0222 is a sobering reminder that even basic management protocols like SNMP, when misconfigured or left unpatched, can disrupt critical automation devices. If you manage Schneider Electric Modicon M340 controllers, apply updates, lock down your networks, and always verify exposure to remote protocols. Prevention is easier than restoring operations after a successful attack.

If you have more questions about this vulnerability or the security of your automation system, always consult with trusted ICS cybersecurity professionals.


*This article is exclusive content created for educational and defensive awareness purposes only.*

Timeline

Published on: 11/22/2022 13:15:00 UTC
Last modified on: 11/30/2022 20:38:00 UTC