CVE-2026-55591

MEDIUMPre-NVD 5.85.8
EchelonGraph scoreLOW confidence

This medium-severity CVE scores 5.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: secondary
Elevated
5.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.8Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Signal K Server is a server application that runs on a central hub in a boat. Prior to 2.28.0, makeRemoteRequest() in src/serverroutes.ts accepted attacker-controlled host, port, useTLS, and selfsignedcert parameters from the testSignalKConnection, requestAccess, and checkAccessRequest endpoints without validating the destination. When security was not configured, addAdminMiddleware() was a no-op in dummysecurity.ts, leaving all three endpoints accessible without authentication. The server could be forced to contact loopback, private, link-local, cloud metadata, or arbitrary external destinations, and selfsignedcert could disable certificate verification for outbound HTTPS requests. The checkAccessRequest endpoint also interpolated requestId into its destination path, allowing traversal to other paths on the selected host. Distinct success, connection-refused, and timeout responses enabled internal port scanning; returned response bodies enabled cloud metadata and internal-service data exfiltration; requestAccess enabled server-side POST requests with attacker-controlled JSON; and access to cluster-internal services could support lateral movement. This issue is fixed in version 2.28.0.

CVSS v3
5.8
EG Score
5.8(low)
EG Risk
57(Attend)
EG Risk 57/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity58% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
0%
EPSS %ILE
20%
KEV
Not listed

Published

June 18, 2026

Last Modified

September 15, 2026

Advisory Details (3)

Auto-updated Sep 15, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

v2.28.0

Patch available: SignalK/signalk-server v2.28.0

https://github.com/SignalK/signalk-server/releases/tag/v2.28.0
github_commit Patch Available

commit 2816b0dda1bd (SignalK/signalk-server)

Patch available: SignalK/signalk-server v2.28.0 (contains commit 2816b0dda1bd)

https://github.com/SignalK/signalk-server/commit/2816b0dda1bdde893d85c969a9c5950e7825eee7
github Patch Available🟡 PoC Available

Server-Side Request Forgery via Remote Connection Endpoints · Advisory · SignalK/signalk-server · GitHub

https://github.com/SignalK/signalk-server/security/advisories/GHSA-q59x-jc9f-gfqf

Vendor Advisories for CVE-2026-55591(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
signalk-server—2.28.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 6× in last 7d / 6× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-17 19:31 UTCEPSS rescore
  3. 2026-09-16 14:08 UTCEPSS rescore
  4. 2026-09-15 18:37 UTCEG score recompute
  5. 2026-09-15 17:29 UTCEG score recompute
  6. 2026-09-15 16:36 UTCEG score recompute
  7. 2026-07-31 03:50 UTCEG score recompute
  8. 2026-07-26 17:17 UTCEG score recompute
  9. 2026-07-23 03:20 UTCEG score recompute
  10. 2026-06-18 21:44 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-55591?
CVE-2026-55591 is a medium vulnerability published on June 18, 2026. Signal K Server is a server application that runs on a central hub in a boat. Prior to 2.28.0, makeRemoteRequest() in src/serverroutes.ts accepted attacker-controlled host, port, useTLS, and selfsignedcert parameters from the testSignalKConnection, requestAccess, and checkAccessRequest endpoints…
When was CVE-2026-55591 disclosed?
CVE-2026-55591 was first published in the National Vulnerability Database on June 18, 2026, with the most recent update on September 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55591 actively exploited?
CVE-2026-55591 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 80.0% of all scored CVEs.
What is the CVSS score of CVE-2026-55591?
CVE-2026-55591 has a CVSS v3 base score of 5.8 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-55591?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55591, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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