CVE-2026-55591

MEDIUMPre-NVD 5.85.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 5.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (20th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated
5.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.8Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
5.8MEDIUMmedium confidence
EG Risk
57
EG Risk 57/100

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 (value × EchelonGraph’s weight)
Severity58% × 45%
The EG Score, 5.8 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
20th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

June 18, 2026

Last Modified

September 30, 2026

Advisory Details (3)

Auto-updated Sep 15, 2026
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 advisoryMentions a patch (unverified)

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 rangeFix by version rangeDependents
signalk-server—
  • every version up to 2.28.0: fixed in 2.28.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 31× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  2. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  3. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  4. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  5. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  6. 2026-10-12 15:55 UTCEG score recompute
  7. 2026-10-11 19:38 UTCEG score recompute
  8. 2026-10-11 16:54 UTCEG score recompute
  9. 2026-10-11 14:17 UTCEG score recompute
  10. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  11. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  12. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  13. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  14. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  15. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  16. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  17. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  18. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  19. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  20. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  21. 2026-09-30 18:12 UTCEG score recompute
  22. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  23. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  24. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  25. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 20th percentile
Show 14 more
  1. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  2. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  3. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  4. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  5. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  6. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  7. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  8. 2026-09-15 18:37 UTCEG score recompute
  9. 2026-09-15 17:29 UTCEG score recompute
  10. 2026-09-15 16:36 UTCEG score recompute
  11. 2026-07-31 03:50 UTCEG score recompute
  12. 2026-07-26 17:17 UTCEG score recompute
  13. 2026-07-23 03:20 UTCEG score recompute
  14. 2026-06-18 21:44 UTCEG score recompute

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-55591?
CVE-2026-55591 is a medium-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-55591 published?
The CVE record for CVE-2026-55591 was published on June 18, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 30, 2026; the record at its source may have been updated since.
Is CVE-2026-55591 actively exploited?
CVE-2026-55591 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (20th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55591?
CVE-2026-55591 has a CVSS base score of 5.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55591?
A fix for CVE-2026-55591 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55591 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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