CVE-2026-39320 is a high-severity uncontrolled resource consumption vulnerability in signalk-server (npm), affecting versions < 2.25.0. It is fixed in 2.25.0.
Summary 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. Description The vulnerability stems from flawed string-to-regex conversion in signalk-server/src/subscriptionmanager.ts. The contextMatcher() and pathMatcher() functions convert wildcard strings (e.g., ) into regular expressions to match incoming data against client subscriptions. While the code attempts to escape . and characters, it fails to escape other dangerous regular expression metacharacters, such as +, (, ), ?, [, and ]. Because of this, an attacker can submit a crafted context that contains nested quantifiers (e.g., ([a-z0-9:-]+)+!). When the server attempts to test this malicious regex against legitimate, lengthy data identifiers (like vessels.urn:mrn:signalk:uuid:d384dc156010), the regex engine fails to find a match at the end of the string but initiates billions of catastrophic backtracking operations trying to resolve the nested combinations. Since Node.js runs on a single-threaded event loop, this locks up the thread indefinitely. Affected Code Blocks & Files File: signalk-server/src/subscriptionmanager.ts Affected lines for Context subscriptions (282-300): Affected lines for Path subscriptions (276-280): Proof of Concept (PoC) Steps <img width="1003" height="524" alt="Screenshot 2026-03-29 101918" src="https://github.com/user-attachments/assets/4b257c4c-f97a-4812-b812-ce2f235b6039" /> Impact This vulnerability achieves a complete Denial of Service (DoS) against the SignalK server. A single unauthenticated WebSocket connection can send the catastrophic payload, which permanently locks the main Node.js event loop. <img width="999" height="153" alt="Screenshot 2026-03-29 101820" src="https://github.com/user-attachments/assets/54214d1c-252f-4533-ad02-14959ea2bed0" />
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2026-39320 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (2.25.0). Upgrading removes the vulnerable code path.
npm
signalk-server (< 2.25.0)signalk-server → 2.25.0 (npm)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-39320 is reachable in your applications. Explore open-source security for your team.
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Upgrade signalk-server to 2.25.0 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-39320 is a high-severity uncontrolled resource consumption vulnerability in signalk-server (npm), affecting versions < 2.25.0. It is fixed in 2.25.0. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
CVE-2026-39320 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
signalk-server (npm) versions < 2.25.0 is affected.
Yes. CVE-2026-39320 is fixed in 2.25.0. Upgrade to this version or later.
Whether CVE-2026-39320 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade signalk-server to 2.25.0 or later.