CVE-2026-22542 is a vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) affecting EFACEC QC 60/90/120 devices, specifically version 8. The flaw allows an attacker with access to the system's internal network to cause a denial of service (DoS) by establishing two concurrent connections via the Telnet service. The vulnerability arises because the device does not properly limit or manage resource allocation for Telnet connections, enabling resource exhaustion with minimal effort. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H) indicates that the attack can be performed remotely over the network without authentication or user interaction, with a high impact on availability. The lack of authentication and the low complexity of the attack make this vulnerability particularly dangerous in environments where the internal network is accessible to potential attackers. EFACEC QC series devices are commonly used in industrial control systems, energy management, and critical infrastructure sectors, where availability is paramount. Although no public exploits have been reported yet, the critical severity score and the nature of the vulnerability suggest that exploitation could lead to significant operational disruptions. The absence of patch links indicates that a fix may not yet be available, emphasizing the importance of interim mitigations.

The primary impact of CVE-2026-22542 is denial of service, which can disrupt the availability of EFACEC QC 60/90/120 devices. For European organizations, especially those in critical infrastructure sectors such as energy, manufacturing, and transportation, this could lead to operational downtime, safety risks, and financial losses. Disruption of these devices could affect industrial control systems and energy distribution networks, potentially causing cascading failures or service interruptions. The vulnerability's ease of exploitation without authentication means that insider threats or lateral movement by attackers who have breached internal networks could quickly leverage this flaw. The lack of user interaction and the minimal resource requirement to trigger the DoS increase the likelihood of successful attacks. This could undermine trust in industrial automation and control environments, leading to regulatory and compliance challenges under European cybersecurity frameworks such as NIS2.

1. Immediately restrict access to the internal network segments hosting EFACEC QC 60/90/120 devices, ensuring only trusted and authorized systems can communicate with them. 2. Disable the Telnet service on affected devices if possible, or replace it with more secure protocols like SSH. 3. Implement network-level controls such as firewalls and intrusion detection/prevention systems to monitor and block multiple concurrent Telnet connections from the same source. 4. Conduct regular network traffic analysis to detect unusual connection patterns indicative of exploitation attempts. 5. Engage with EFACEC support or vendors to obtain patches or firmware updates as soon as they become available. 6. Develop and test incident response plans specifically addressing denial of service scenarios affecting industrial control devices. 7. Segment industrial control networks from corporate IT networks to limit attacker movement and exposure. 8. Educate internal teams about the risks of this vulnerability and the importance of internal network security hygiene.