SignalK signalk-server, a server application used on central hubs in boats, suffers from an authentication bypass vulnerability identified as CVE-2025-69203, affecting versions prior to 2.19.0. The vulnerability stems from two main issues: first, the server trusts the X-Forwarded-For HTTP header without validation to determine the client's IP address. This header is intended to preserve the original client IP when requests pass through reverse proxies, but unconditional trust allows attackers to spoof their IP address. Second, the admin UI prominently displays the 'description' field of access requests but less prominently or separately shows the 'permissions' field, which controls access levels. An attacker can exploit this by submitting an access request with a description suggesting readonly access while requesting admin permissions. Additionally, an information disclosure vulnerability allows enumeration of device/source names, enabling attackers to impersonate legitimate devices. By combining these factors, an attacker can craft highly convincing social engineering attacks: spoofing trusted internal IPs, impersonating devices, and submitting misleading descriptions to trick administrators into granting elevated privileges. The vulnerability requires user interaction (administrator approval) but no prior authentication, and the CVSS score is 6.3, reflecting medium severity with low complexity of attack and partial impact on confidentiality, integrity, and availability. The issue is resolved in version 2.19.0 by correcting header validation and improving UI clarity to prevent spoofing and deception.

For European organizations operating maritime vessels or managing marine IoT infrastructure using SignalK signalk-server, this vulnerability poses a significant risk. Unauthorized attackers can gain administrative access to central boat hubs, potentially allowing manipulation or disruption of navigation, communication, or sensor data. This could lead to compromised vessel safety, data integrity issues, and operational disruptions. The social engineering aspect increases the likelihood of successful exploitation, especially in environments where administrators may not be fully trained to detect spoofed requests. Confidentiality is impacted through device impersonation and information disclosure, integrity is threatened by unauthorized permission escalation, and availability could be affected if attackers disrupt server operations. Given the maritime industry's importance in Europe, including commercial shipping, fishing, and recreational boating, exploitation could have economic and safety consequences. However, the requirement for administrator interaction somewhat limits automated exploitation, making targeted attacks more probable than widespread automated compromise.

European organizations should prioritize upgrading all instances of signalk-server to version 2.19.0 or later, which addresses the vulnerability by validating the X-Forwarded-For header and improving the admin UI to clearly display permission requests. Administrators should be trained to scrutinize access requests carefully, especially those requesting elevated permissions, and to verify the legitimacy of device identities through out-of-band methods. Network segmentation should be enforced to limit access to the signalk-server admin interface only to trusted internal networks and VPNs. Implementing strict logging and monitoring of access requests and approvals can help detect suspicious activity. Additionally, disabling or restricting the use of the X-Forwarded-For header where possible, or configuring reverse proxies to sanitize or overwrite this header, can reduce spoofing risks. Organizations should also review and patch any related information disclosure vulnerabilities to prevent device enumeration that aids attackers. Finally, instituting multi-factor authentication for administrative actions can add an extra layer of defense against social engineering attacks.