CVE-2022-37301 is a high-severity vulnerability classified as CWE-191 (Integer Underflow) affecting multiple Schneider Electric Modicon programmable logic controllers (PLCs), including the Modicon M340 CPU (BMXP34* series, version 3.40 and prior), Modicon M580 CPU (BMEP* and BMEH* series, version 3.22 and prior), Legacy Modicon Quantum/Premium (all versions), Modicon Momentum MDI (171CBU* series, all versions), and Modicon MC80 (BMKC80, version 1.7 and prior). The vulnerability arises from an integer underflow condition during processing of Modbus TCP protocol communications. Specifically, an attacker can craft malicious Modbus TCP packets that trigger an integer underflow, causing wraparound in memory calculations. This results in memory access violations that lead to a denial of service (DoS) condition on the affected PLCs, effectively disrupting their control operations. The vulnerability requires no authentication or user interaction and can be exploited remotely over the network (CVSS vector: AV:N/AC:L/PR:N/UI:N). The impact is limited to availability, with no direct confidentiality or integrity compromise reported. No known exploits are currently observed in the wild, but the ease of exploitation combined with the critical role of these PLCs in industrial control systems (ICS) makes this a significant threat. The Modicon M340 and related PLCs are widely used in industrial automation environments, including manufacturing, energy, water treatment, and critical infrastructure sectors. Disruption of these controllers can halt industrial processes, cause safety hazards, and lead to significant operational and financial losses.

For European organizations, the impact of CVE-2022-37301 is substantial due to the widespread deployment of Schneider Electric Modicon PLCs in critical infrastructure and industrial sectors. A successful exploitation can cause denial of service on key control systems, leading to process downtime, safety risks, and potential cascading failures in automated environments. Sectors such as manufacturing, energy production and distribution, water and wastewater management, and transportation are particularly vulnerable. The disruption of PLC operations may also affect supply chains and critical services, amplifying economic and societal consequences. Given the vulnerability requires no authentication and can be triggered remotely, attackers with network access could cause outages without needing insider privileges. Although no data integrity or confidentiality loss is indicated, availability impacts in ICS environments often translate into severe operational and safety risks. European organizations with legacy or unpatched Modicon devices are at higher risk, especially those with network exposure of Modbus TCP services or insufficient network segmentation.

1. Immediate patching or firmware updates from Schneider Electric should be applied once available to address the integer underflow condition. 2. Network segmentation: Isolate PLCs from general IT networks and restrict Modbus TCP traffic to trusted management stations only. 3. Implement strict firewall rules to block unauthorized Modbus TCP packets from untrusted sources. 4. Deploy intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection for Modbus protocol to identify and block malformed packets that could exploit this vulnerability. 5. Conduct regular network scans to identify exposed Modbus TCP services and remediate unnecessary exposure. 6. Employ network access control (NAC) to limit devices that can communicate with PLCs. 7. Monitor PLC operational status and logs for signs of unexpected resets or communication failures indicative of exploitation attempts. 8. Develop and test incident response plans specific to ICS availability disruptions. 9. For legacy devices where patches are unavailable, consider compensating controls such as air-gapping or physical network isolation. 10. Engage with Schneider Electric support to obtain guidance and updates on mitigation and patch availability.