CVE-2022-3480 is a high-severity vulnerability affecting PHOENIX CONTACT FL MGUARD and TC MGUARD devices running firmware versions below 8.9.0. The vulnerability is classified under CWE-770, which pertains to the allocation of resources without limits or throttling. Specifically, an unauthenticated remote attacker can exploit this flaw by initiating a large number of unauthenticated HTTPS connections from multiple source IP addresses. This flood of connections leads to resource exhaustion on the affected devices, causing a denial-of-service (DoS) condition. Notably, conventional mitigation strategies such as configuring firewall limits on incoming connections are ineffective against this attack vector, as the vulnerability stems from the device's internal handling of connection requests rather than external traffic filtering. The vulnerability does not impact confidentiality or integrity but severely affects availability, rendering the devices unresponsive or inoperable. The CVSS v3.1 base score is 7.5, reflecting a high severity due to the ease of exploitation (no authentication or user interaction required), network attack vector, and the significant impact on availability. No known exploits have been reported in the wild as of the publication date (November 15, 2022). The affected products are critical industrial network security devices used to protect and manage secure remote access and firewalling in industrial control systems and critical infrastructure environments.

For European organizations, the impact of CVE-2022-3480 can be substantial, especially for those operating critical infrastructure, manufacturing plants, energy utilities, and industrial automation environments that rely on PHOENIX CONTACT FL MGUARD and TC MGUARD devices for secure network segmentation and remote access. A successful DoS attack could disrupt operational technology (OT) networks, leading to downtime, loss of monitoring and control capabilities, and potential safety risks. The inability to mitigate the attack via firewall limits increases the risk of prolonged outages. This could affect supply chains, energy distribution, and industrial processes, resulting in financial losses and reputational damage. Since these devices are often deployed in environments requiring high availability and robust security, the vulnerability poses a direct threat to operational continuity and resilience against cyberattacks. Additionally, the unauthenticated nature of the attack vector means that threat actors do not need credentials or insider access, broadening the potential attacker base.

1. Immediate firmware upgrade to version 8.9.0 or later where the vulnerability is patched is the most effective mitigation. Organizations should prioritize patch management for all affected devices. 2. Implement network segmentation to isolate FL MGUARD and TC MGUARD devices from untrusted networks and limit exposure to the internet or large untrusted IP address spaces. 3. Deploy intrusion detection and prevention systems (IDS/IPS) capable of detecting anomalous HTTPS connection floods targeting these devices and block suspicious traffic patterns before reaching the devices. 4. Use rate limiting and connection throttling at upstream network devices (e.g., routers, switches) that can enforce limits on the number of new connections per source IP or aggregate connections, compensating for the inability of the device itself to do so. 5. Monitor device logs and network traffic for unusual spikes in HTTPS connection attempts and establish alerting mechanisms for early detection of potential DoS attempts. 6. Engage with PHOENIX CONTACT support and subscribe to vendor security advisories to stay informed about patches and recommended configurations. 7. For critical environments, consider deploying redundant or failover devices to maintain availability during an attack or maintenance window.