Zyxel Patches Critical Router Flaw Amid New OT Cyber Threat Scoring System

A critical vulnerability affecting over a dozen Zyxel router models has been addressed through security updates, just as a new model for measuring the severity of operational technology (OT) cyber incidents has been introduced. The developments highlight the evolving landscape of cybersecurity threats and the need for more effective assessment and mitigation strategies.

The vulnerability, tracked as CVE-2025-13942, is a command injection security flaw found in the UPnP function of various Zyxel 4G LTE/5G NR CPE, DSL/Ethernet CPE, Fiber ONTs, and wireless extenders. According to Zyxel, unauthenticated remote attackers can exploit this flaw to execute operating system (OS) commands on an affected device using maliciously crafted UPnP SOAP requests.

However, the likelihood of successful exploitation is reduced by the fact that WAN access is disabled by default on these devices, and the attack can only be carried out remotely if both WAN access and the vulnerable UPnP function have been enabled. "It is important to note that WAN access is disabled by default on these devices, and the attack can be carried out remotely only if both WAN access and the vulnerable UPnP function have been enabled," Zyxel said in a statement.

Meanwhile, a new model for measuring the severity of OT cyber incidents has been devised by ICS/OT experts. Dubbed the "Richter Scale," this scoring system aims to bring clarity to the assessment of cybersecurity events in operational technology environments. The model provides a standardized framework for evaluating the magnitude and impact of OT cyber incidents, allowing for more effective incident response and mitigation strategies.

The introduction of the Richter Scale model comes at a time when OT cybersecurity threats are becoming increasingly sophisticated and frequent. As the Zyxel vulnerability demonstrates, even seemingly minor flaws can have significant consequences if left unaddressed. By providing a standardized framework for assessing and mitigating OT cyber incidents, the Richter Scale model has the potential to improve the overall resilience of operational technology environments.

In the context of the Zyxel vulnerability, the Richter Scale model could provide valuable insights into the potential impact of a successful attack. By evaluating the severity of the vulnerability and the potential consequences of exploitation, organizations can better prioritize their incident response efforts and allocate resources more effectively.

As the cybersecurity landscape continues to evolve, the need for effective assessment and mitigation strategies will only continue to grow. The introduction of the Richter Scale model and the patching of critical vulnerabilities like CVE-2025-13942 represent important steps towards improving the resilience of operational technology environments and reducing the risk of cyber incidents.