CVE-2024-8419 is a vulnerability classified under CWE-306 (Missing Authentication for Critical Function) affecting the ifm Smart PLC AC402s, a programmable logic controller widely used in industrial automation. The vulnerability exists because a network-accessible endpoint hosts a script that lacks any authentication mechanism, allowing an unauthenticated remote attacker to invoke a fail-safe state on the device. This fail-safe state is a protective mode intended to prevent damage or unsafe conditions but effectively results in a denial of service by halting normal PLC operations. The affected firmware versions are 4.04 and 6.1.8. The CVSS v3.1 score is 7.5 (high), reflecting that the attack vector is network-based (AV:N), requires no privileges (PR:N), no user interaction (UI:N), and impacts availability (A:H) without compromising confidentiality or integrity. The scope remains unchanged (S:U), meaning the impact is limited to the vulnerable device itself. No patches have been published at the time of disclosure, and no exploits are known to be active in the wild. The vulnerability poses a significant risk to industrial environments relying on these PLCs for critical control functions, as attackers could remotely disrupt operations without detection or authentication barriers.

For European organizations, especially those in manufacturing, automotive, and industrial automation sectors, this vulnerability could lead to unexpected shutdowns or interruptions in production lines controlled by the ifm Smart PLC AC402s. The fail-safe state, while protective, halts normal operations, potentially causing significant downtime and financial losses. Since PLCs are integral to operational technology (OT) environments, disruptions could cascade, affecting supply chains and critical infrastructure. The lack of authentication means attackers can exploit this remotely without insider access, increasing the risk of opportunistic or targeted attacks. Although confidentiality and integrity are not directly impacted, the availability impact alone can have severe operational consequences. The absence of known exploits currently provides a window for mitigation, but the ease of exploitation and critical function affected make this a pressing concern for European industrial entities.

1. Immediately implement network segmentation to isolate the ifm Smart PLC AC402s devices from general IT networks and restrict access to trusted management stations only. 2. Employ strict firewall rules and access control lists (ACLs) to block unauthorized inbound traffic to the PLC management interfaces. 3. Monitor network traffic for unusual or unauthorized commands targeting the PLC endpoints, using intrusion detection systems (IDS) tailored for industrial protocols. 4. Coordinate with ifm electronic GmbH to obtain and apply firmware updates or patches as soon as they become available. 5. Conduct regular security audits of OT environments to identify exposed PLCs and verify that authentication mechanisms are enforced where possible. 6. Implement compensating controls such as VPNs or secure tunnels for remote access to PLCs to add an authentication layer. 7. Train OT personnel on the risks of unauthenticated access and encourage prompt reporting of anomalies. 8. Develop and test incident response plans specifically addressing PLC availability disruptions to minimize downtime in case of exploitation.