CVE-2026-55591: SSRF (CVSS 5.8)

Description

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.

Is your site exposed to CVE-2026-55591?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

5.8

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

EPSS — Exploit Prediction

0.0027

Probability of exploitation

0.20%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-918 Server-Side Request Forgery (SSRF)

References

Other References

https://github.com/SignalK/signalk-server/commit/2816b0dda1bdde893d85c969a9c5950e7825eee7 https://github.com/SignalK/signalk-server/releases/tag/v2.28.0 https://github.com/SignalK/signalk-server/security/advisories/GHSA-q59x-jc9f-gfqf https://github.com/SignalK/signalk-server/security/advisories/GHSA-q59x-jc9f-gfqf

Frequently Asked Questions

What is CVE-2026-55591? +

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. It has a CVSS v3.1 base score of 5.8 (MEDIUM).

How severe is CVE-2026-55591? +

CVE-2026-55591 has a CVSS v3.1 score of 5.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0027, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-55591? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-77069

n8n before 1.123.69, 2.33.4, and 2.34.1 contains an SSRF protection bypass in the OAuth2 credential authorization-code-to-access-token exchange. While OAuth2 discovery …

CVE-2026-42336

MaxKB is an open-source AI assistant for enterprise. MaxKB 2.8.0 and prior are vulnerable to a server-side request forgery (SSRF) …

CVE-2026-41682

pupnp is an SDK for development of UPnP device and control point applications. Prior to version 1.18.5, pupnp is vulnerable …

CVE-2026-44286

FastGPT is an AI Agent building platform. Prior to version 4.14.17, an unauthenticated Server-Side Request Forgery (SSRF) vulnerability allows attackers …

CVE-2026-41172

Squidex is an open source headless content management system and content management hub. Prior to version 7.23.0, an SSRF vulnerability …

CVE-2026-45412

MaxKB is an open-source AI assistant for enterprise. Prior to 2.9.1, SSRF via work_flow_template Import. Authenticated users can supply arbitrary …

CVE-2026-55591