CVE-2026-39320: Signal K Server has an Unauthenticated Regular Expression Denial of Service (ReDoS) via WebSocket Subscription Paths

The SignalK server is vulnerable to an unauthenticated Regular Expression Denial of Service (ReDoS) attack within its WebSocket subscription handling logic. By injecting unescaped regex metacharacters into the context parameter of a stream subscription, an attacker can force the server’s Node.js event loop into a catastrophic backtracking loop when evaluating long string identifiers (like the server’s self UUID). This results in a total Denial of Service (DoS) where the server CPU spikes to 100% and becomes completely unresponsive to further API or socket requests.