CVE-2025-3116 is a high-severity vulnerability affecting Schneider Electric Modicon Controllers M241 and M251, specifically versions prior to 5.3.12.51. The vulnerability is classified under CWE-20, which pertains to improper input validation. An authenticated malicious user can exploit this flaw by sending specially crafted malformed HTTPS requests with improperly formatted body data to the controller. This improper input validation can cause the controller to enter a Denial of Service (DoS) state, disrupting its normal operation. The vulnerability does not require user interaction and can be exploited remotely over the network (AV:N), with low attack complexity (AC:L). The attacker must have some level of privileges (PR:L), but no additional authentication tokens or user interaction are needed. The vulnerability impacts the availability of the affected controllers, potentially halting industrial processes or automation systems that rely on these devices. No known exploits are currently reported in the wild, but the high CVSS score of 7.1 indicates a significant risk if exploited. The lack of patch links suggests that remediation might require coordination with Schneider Electric or awaiting an official firmware update. Given the critical role of Modicon controllers in industrial control systems, this vulnerability poses a serious threat to operational continuity and safety in environments using these devices.

For European organizations, the impact of CVE-2025-3116 could be substantial, particularly in sectors reliant on industrial automation such as manufacturing, energy, utilities, and critical infrastructure. A successful DoS attack on Modicon M241/M251 controllers could lead to production downtime, safety system failures, and potential cascading effects on supply chains. The disruption of industrial processes could result in financial losses, regulatory non-compliance, and damage to reputation. Additionally, since these controllers are often part of critical infrastructure, prolonged outages could have broader societal impacts. The requirement for authenticated access somewhat limits the attack surface but does not eliminate risk, especially in environments where network segmentation or access controls are insufficient. European organizations with legacy or unpatched Schneider Electric controllers are particularly vulnerable, emphasizing the need for immediate risk assessment and mitigation.

1. Immediate assessment of all Schneider Electric Modicon M241/M251 controllers in the network to identify versions prior to 5.3.12.51. 2. Coordinate with Schneider Electric for official patches or firmware updates addressing CVE-2025-3116 and apply them as soon as they become available. 3. Implement strict network segmentation and access controls to limit authenticated access to the controllers only to trusted and necessary personnel or systems. 4. Employ robust authentication mechanisms and monitor authentication logs for unusual access patterns that could indicate exploitation attempts. 5. Use deep packet inspection or application-layer firewalls to detect and block malformed HTTPS requests targeting the controllers. 6. Regularly audit and update industrial control system (ICS) security policies to incorporate vulnerability management and incident response plans specific to these controllers. 7. Conduct employee training focused on secure handling of ICS devices and awareness of potential exploitation vectors. 8. Consider deploying anomaly detection systems tailored for ICS environments to identify early signs of DoS or other malicious activities.