A failure to secure the firmware partition fallback process in Phoenix Contact CHARX devices allows unauthenticated attackers to gain unauthorized access via default credentials.

The devices exhibit a fail-open behavior (CWE-636) where an unauthenticated remote attacker can force a transition to a legacy or secondary firmware partition. This partition contains insecure configurations, specifically the use of default credentials, which can be exploited for unauthorized access.

The CVSS score of 8.6 indicates a high risk of unauthorized access and potential loss of availability. By forcing the system to a less secure state, attackers can bypass current authentication mechanisms, leading to complete device control, data exfiltration, or the disabling of charging operations.

Immediate Action: Update the affected CHARX devices to firmware version 1.9.1 or later.

Proactive Monitoring: Monitor device logs for unexpected partition changes or attempts to authenticate with default credentials.

Compensating Controls: Ensure that management interfaces are isolated from public networks and that all default passwords are changed on all accessible partitions.

Public Exploit Available: No (exploit_available: false)

The reliance on default credentials in legacy firmware partitions presents a significant security gap. Administrators must prioritize the upgrade to version 1.9.1 to ensure that the device does not fall back to an insecure state, thereby mitigating the risk of unauthorized administrative access.