CVE-2026-55591Signal K Server: Server-Side Request Forgery via Remote Connection Endpoints
- 5.8MediumCVSS base score
- 0.30%Exploitation in 30 daysEPSS · top 77% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- YesPublic exploitsa reference or SSVC says so
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.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. A reference of the record is tagged as an exploit. CISA's SSVC rates its exploitation: a proof of concept is public.
Show the exploits1
References tagged exploit1 reference
- https://github.com/SignalK/signalk-server/security/advisories/GHSA-q59x-jc9f-gfqf (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
- 3 months later
· 3 months later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N |
| NVDNVD · Deferred | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N |
- EPSS (exploitation in 30 days)
- 0.30% · top 77% of all CVEs (12 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.8.
Affected products
- affected < 2.28.0
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- npmsignalk-serverGHSA-q59x-jc9f-gfqf (opens in a new tab)
References
References3
- https://github.com/SignalK/signalk-server/security/advisories/GHSA-q59x-jc9f-gfqf (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/SignalK/signalk-server/commit/2816b0dda1bdde893d85c969a9c5950e7825eee7 (opens in a new tab)x_refsource_MISC
- https://github.com/SignalK/signalk-server/releases/tag/v2.28.0 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-78677 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-q59x-jc9f-gfqf (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-55591)Record last updated .