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TI-2026-40128 Aliases CVE-2026-55591GHSA-q59x-jc9f-gfqf

Signal K Server: Server-Side Request Forgery via Remote Connection Endpoints

Priority HIGH 65CWE-918Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Information disclosure
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-918 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00298 22nd percentileScored 2026-11-07
Fix Fixed signalk-server (SignalK): 2.28.0signalk-server (npm): 2.28.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
SignalKsignalk-serverbefore 2.28.02.28.0Patch availableCNA
—signalk-server (npm)before 2.28.02.28.0Patch availableGHSA-q59x-jc9f-gfqf
  • signalk-server VendorSignalK Affected before 2.28.0 Fixed in 2.28.0 Patch available CNA
  • signalk-server (npm) Vendor— Affected before 2.28.0 Fixed in 2.28.0 Patch available GHSA-q59x-jc9f-gfqf

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:signalk:signal_k_server:*:*:*:*:*:*:*:*——SignalK
  • cpe:2.3:a:signalk:signal_k_server:*:*:*:*:*:*:*:* Versions — — ·SignalK

Remediation

  • Fix · CNA signalk-server (SignalK) Fixed in 2.28.0
  • Fix · GHSA-q59x-jc9f-gfqf signalk-server (npm) Fixed in 2.28.0 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55591
  2. 2026-10-03 Alias added: GHSA-q59x-jc9f-gfqf

References

Other 4

  • TI-2026-26300 signalk-server: Privilege Escalation by Admin Role Injection via /enableSecurity CVSS 3.1CRITICAL 9.4
  • TI-2025-40835 Signal K Server has Unauthenticated State Pollution leading to Remote Code Execution (RCE) CVSS 3.1CRITICAL 9.7
  • TI-2025-42138 Signal K Server vulnerable to JWT Token Theft via WebSocket Enumeration and Unauthenticated Polling CVSS 3.1CRITICAL 9.1
  • TI-2026-30295 Signal K Server's WebSocket Login Endpoint Lacks Rate Limiting (Credential Brute-Force) CVSS 4.0HIGH 8.7
  • TI-2025-42657 Signal K Server Vulnerable to Access Request Spoofing CVSS 3.1HIGH 8.8
  • TI-2026-18939 RCE - Command Injection in Signal K set-system-time plugin CVSS 3.1CRITICAL 10.0
See all 16 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences