SignalK Server is a server application designed to run on a central hub in marine vessels, facilitating data exchange and management. Prior to version 2.24.0, the server contained an input validation flaw classified under CWE-20 (Improper Input Validation), CWE-125 (Out-of-bounds Read), and CWE-200 (Exposure of Sensitive Information). Specifically, the vulnerability arises from insufficient filtering of the 'from' field in requests, which allows a low-privileged authenticated user to bypass prototype boundary protections. By exploiting this, an attacker can perform an arbitrary prototype read, accessing internal functions and properties from the global prototype object. This breaks the intended data isolation model, potentially exposing sensitive internal data that should not be accessible to such users. The flaw does not require user interaction and can be exploited remotely over the network, given authentication. The vulnerability has been assigned CVE-2026-35038 and carries a CVSS 4.0 base score of 2.1, reflecting low severity due to limited impact and the requirement for authentication. The issue was addressed and patched in SignalK Server version 2.24.0. There are no known public exploits or active exploitation campaigns reported at this time.

The primary impact of this vulnerability is unauthorized disclosure of internal server data due to prototype pollution read access. While it does not allow code execution or privilege escalation, the exposure of internal functions and properties can aid attackers in reconnaissance or facilitate further attacks if combined with other vulnerabilities. For organizations operating marine vessels using SignalK Server, this could lead to leakage of sensitive operational data or internal server state, potentially compromising operational security. However, the requirement for authenticated access and the low CVSS score limit the scope and severity of impact. The vulnerability does not affect availability or integrity directly but undermines confidentiality. Given the niche deployment of SignalK Server in marine environments, the overall impact is moderate but should not be ignored, especially for critical maritime operations relying on secure data isolation.

The most effective mitigation is to upgrade SignalK Server to version 2.24.0 or later, where this vulnerability has been patched. Organizations should implement strict access controls to limit authenticated user privileges, minimizing the risk from low-privileged users. Additionally, monitoring and logging of access to the 'from' field or suspicious prototype-related requests can help detect exploitation attempts. Developers and administrators should review input validation mechanisms to ensure robust prototype boundary enforcement and avoid similar prototype pollution issues. Employing runtime application self-protection (RASP) or web application firewalls (WAFs) with custom rules targeting prototype pollution patterns may provide additional defense layers. Regular security audits and code reviews focusing on input validation and prototype handling are recommended to prevent recurrence.