CVE-2025-41696 identifies a vulnerability in the Phoenix Contact FL SWITCH 2005, a network switch commonly used in industrial automation environments. The root cause is the presence of hardcoded user credentials embedded within the device’s firmware, classified under CWE-798. An attacker can exploit an undocumented UART (Universal Asynchronous Receiver/Transmitter) port on the printed circuit board (PCB) as a side-channel to access the device. By leveraging the hardcoded credentials previously disclosed in CVE-2025-41692, the attacker can gain read-only access to portions of the device’s filesystem. This access could allow the attacker to extract sensitive information such as configuration files, network settings, or other operational data that could facilitate further attacks or reconnaissance. The vulnerability has a CVSS v3.1 base score of 4.6, reflecting medium severity, with an attack vector classified as physical (AV:P), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact is limited to confidentiality (C:H), with no integrity or availability impact. No patches or mitigations have been published yet, and no exploits are known in the wild. The vulnerability highlights the risks of embedded hardcoded credentials and undocumented hardware interfaces in industrial control devices, which can be leveraged as attack vectors bypassing traditional network defenses.

For European organizations, especially those in critical infrastructure sectors such as manufacturing, energy, and transportation that rely on Phoenix Contact FL SWITCH 2005 devices, this vulnerability poses a confidentiality risk. Unauthorized read access to the filesystem could expose sensitive operational data, network configurations, or credentials that attackers might use to escalate privileges or move laterally within industrial control systems. Although the vulnerability does not directly impact integrity or availability, the information disclosure could facilitate more damaging attacks. The requirement for physical or close network proximity to access the UART port limits remote exploitation but increases risk in environments with insufficient physical security. The lack of patches means organizations must rely on compensating controls to reduce exposure. The vulnerability could also affect supply chain security if these devices are integrated into larger industrial networks across Europe.

1. Implement strict physical security controls to prevent unauthorized access to network devices, especially those in sensitive industrial environments. 2. Conduct hardware audits to identify undocumented interfaces such as UART ports and disable or physically block access where possible. 3. Monitor network traffic and device logs for unusual access patterns or attempts to interact with device management interfaces. 4. Segregate industrial control networks from corporate and external networks using firewalls and network segmentation to limit attacker movement. 5. Engage with Phoenix Contact for updates or firmware patches and apply them promptly once available. 6. Consider replacing affected devices with models that do not contain hardcoded credentials or undocumented interfaces if feasible. 7. Train staff on the risks associated with embedded credentials and hardware side-channels to improve detection and response capabilities.