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CVE-2026-41893 high CVSS 7.5

Vulnerability in signalk-server (CVE-2026-41893)

Summary

Vulnerability in signalk-server (CVE-2026-41893). Data can be tampered with by attackers. Exploitable via POST /login. Mitigation: upgrade to 2.25.0 or later.

Original description

The description as published by the source.

Summary

The HTTP login endpoints (POST /login and POST /signalk/v1/auth/login) are protected by express-rate-limit (default: 100 attempts per 10-minute window, configurable via HTTP_RATE_LIMITS). The WebSocket login path — sending {login: {username, password}} messages over an established WebSocket connection — calls app.securityStrategy.login() directly without any rate limiting.

An attacker can bypass HTTP rate limiting entirely by opening a WebSocket connection and attempting unlimited password guesses at the speed bcrypt allows (~20 attempts/sec with 10 salt rounds).

Details

Vulnerable code: src/interfaces/ws.ts, function processLoginRequest (lines 753-780)

The function directly calls app.securityStrategy.login(msg.login.username, msg.login.password) with no throttling or attempt tracking.

Rate-limited HTTP path for comparison: src/tokensecurity.ts lines 609-617 apply loginLimiter middleware to the HTTP login routes at line 637.

Steps to Reproduce

  1. Start Signal K server with security enabled
  2. Open a WebSocket connection to ws://server:3000/signalk/v1/stream?subscribe=none
  3. Wait for the hello message
  4. Send login attempts in rapid succession: 
    {"requestId": "1", "login": {"username": "admin", "password": "guess1"}}
{"requestId": "2", "login": {"username": "admin", "password": "guess2"}}
  5. Observe that all attempts are processed without any 429 response or throttling
  6. For comparison, send 100+…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-41893 has been found in signalk-server.
Attackers can target a specific entry point like POST /login over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade signalk-server to 2.25.0 or later.
If unsure, ask your IT team or search "signalk-server CVE-2026-41893" on the vendor's site.

CVE-2026-41893 (signalk-server) — CWE-307 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: POST /login / POST /signalk/v1/auth/login / HTTP_RATE_LIMITS / processLoginRequest
Patched: 2.25.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-307) exists in signalk-server. Attackers reach the vulnerable code path via POST /login without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of signalk-server. Attack surface: POST /login / POST /signalk/v1/auth/login / HTTP_RATE_LIMITS / processLoginRequest.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 2.25.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual POST /login requests with malformed payloads or SQL meta-characters. Run grep -r 'signalk-server' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'signalk-server' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で signalk-server を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'POST /login' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /login への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade signalk-server to 2.25.0

    ステージング環境で 2.25.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against POST /login on staging to confirm patch closes the vector

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

npm signalk-server
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.25.0"}]}]

References

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