CVE-2026-39320Public exploitNetwork attack vector

Unauthenticated service hang via unescaped subscription regex

Published Apr 21, 2026 · Updated Apr 21, 2026

Regular expression denial of service in Signal K Server before 2.25.0 allows remote attackers to hang the server via WebSocket subscriptions. The contextMatcher and pathMatcher functions compile incompletely escaped subscription context and path strings as regular expressions, allowing nested quantifiers to trigger catastrophic backtracking. A single unauthenticated WebSocket connection can lock the Node.js event loop, consume a full CPU core, and leave API and socket requests unresponsive.

CVSS severity7.5
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Signal K Server before 2.25.0 allows remote attackers to hang the server via WebSocket subscriptions. The contextMatcher and pathMatcher functions compile incompletely escaped subscription context and path strings as regular expressions, allowing nested quantifiers to trigger catastrophic backtracking. A single unauthenticated WebSocket connection can lock the Node.js event loop, consume a full CPU core, and leave API and socket requests unresponsive.

The record

CVE
CVE-2026-39320
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Signal K
Product
Signal K Server
Classifications
CWE-400, CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.25.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Signal K · Signal K Serverversion=< 2.25.0

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-1333Inefficient Regular Expression Complexity
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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