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

> Unauthenticated attackers can cause a total Denial of Service in Signal K Server by injecting regex metacharacters into WebSocket subscription paths.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Apr 2026
- **Updated:** 21 Apr 2026
- **Also known as:** GHSA-7gcj-phff-2884

## What is CVE-2026-39320?

CVE-2026-39320 is a high-severity denial of service vulnerability in signalk-server, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Signal K Server is a server application that runs on a central hub in a boat. Versions prior to 2.25.0 are vulnerable to an unauthenticated Regular Expression Denial of Service (ReDoS) attack within the 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. Version 2.25.0 contains a fix.

Weakness: CWE-400 (Uncontrolled Resource Consumption), CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2026-39320?

2 open source packages ship an affected version, including signalk-server. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `signalk-server` | npm | All versions | 2.25.0 |
| `signalk-server` | npm | All versions | 2.25.0 |

Products: Signalk Signal K Server.

## How do I fix CVE-2026-39320?

Upgrade signalk-server to 2.25.0 or later.

## Is CVE-2026-39320 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39320 exists.

## Other vulnerabilities in signalk-server

- [CVE-2026-23515](https://insights.sbomify.com/CVE-2026-23515/): RCE - Command Injection in Signal K set-system-time plugin (critical 10.0)
- [CVE-2025-66398](https://insights.sbomify.com/CVE-2025-66398/): Signal K Server has Unauthenticated State Pollution leading to Remote Code Execution (RCE) (critical 9.7)
- [CVE-2026-33950](https://insights.sbomify.com/CVE-2026-33950/): signalk-server: Privilege Escalation by Admin Role Injection via /enableSecurity (critical 9.4)
- [CVE-2025-68620](https://insights.sbomify.com/CVE-2025-68620/): Signal K Server vulnerable to JWT Token Theft via WebSocket Enumeration and Unauthenticated Polling (critical 9.1)
- [CVE-2026-41893](https://insights.sbomify.com/CVE-2026-41893/): Signal K Server's WebSocket Login Endpoint Lacks Rate Limiting (Credential Brute-Force) (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39320 and fix it if it is affected.

What it is: CVE-2026-39320 is a high-severity denial of service vulnerability in signalk-server, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39320 exists.

Affected packages and fixed versions:
- signalk-server (npm): affected all versions; fixed in 2.25.0
- signalk-server (npm): affected all versions; fixed in 2.25.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-39320/ (Markdown: https://insights.sbomify.com/CVE-2026-39320/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39320
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39320
- OSV: https://osv.dev/vulnerability/CVE-2026-39320

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39320/
Summaries are generated and may contain mistakes; the official description above is the record.