SignalK Server up to 2.27.x Remote Request src/serverroutes.ts makeRemoteRequest host/port/useTLS/selfsignedcert server-side request forgery

Summaryinfo

A vulnerability classified as critical was found in SignalK Server up to 2.27.x. Affected is the function makeRemoteRequest of the file src/serverroutes.ts of the component Remote Request Handler. Such manipulation of the argument host/port/useTLS/selfsignedcert leads to server-side request forgery. This vulnerability is listed as CVE-2026-55591. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in SignalK Server up to 2.27.x and classified as critical. Affected by this issue is the function makeRemoteRequest of the file src/serverroutes.ts of the component Remote Request Handler. The manipulation of the argument host/port/useTLS/selfsignedcert with an unknown input leads to a server-side request forgery vulnerability. Using CWE to declare the problem leads to CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-55591 since 06/17/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available.

Upgrading to version 2.28.0 eliminates this vulnerability.

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Productinfo

Vendor

• SignalK

Name

• Server

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13
• 2.14
• 2.15
• 2.16
• 2.17
• 2.18
• 2.19
• 2.20
• 2.21
• 2.22
• 2.23
• 2.24
• 2.25
• 2.26
• 2.27

CPE 2.3info

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CPE 2.2info

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