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CVE-2026-45736 medium CVSS 4.4

Vulnerability in ws (CVE-2026-45736)

Summary

Vulnerability in ws (CVE-2026-45736). Confidential information can be exposed externally. Exploitable via TypedArray. Mitigation: upgrade to 8.20.1 or later.

Original description

The description as published by the source.

Impact

The websocket.close() implementation is vulnerable to uninitialized memory disclosure when a TypedArray is passed as the reason argument.

Proof of concept

import { deepStrictEqual } from 'node:assert';
import { WebSocket, WebSocketServer } from 'ws';

const wss = new WebSocketServer(
  { port: 0, skipUTF8Validation: true },
  function () {
    const { port } = wss.address();
    const ws = new WebSocket(`ws://localhost:${port}`, {
      skipUTF8Validation: true
    });

    ws.on('close', function (code, reason) {
      deepStrictEqual(reason, Buffer.alloc(80));
    });
  }
);

wss.on('connection', function (ws) {
  ws.close(1000, new Float32Array(20));
});

Patches

The vulnerability was fixed in ws@8.20.1 (https://github.com/websockets/ws/commit/c0327ec15a54d701eb6ccefaa8bef328cfc03086).

Credits

Credit for the private and responsible disclosure of this issue goes to Nikita Skovoroda.

Remarks

Although the calculated CVSS severity is medium, the actual severity is believed to be low, as the flaw is only exploitable through misuse that is unlikely in practice.

Resources

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-2026-45736 has been found in ws.
Attackers can target a specific entry point like TypedArray over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 4.4/10.
What to do: upgrade ws to 8.20.1 or later.
If unsure, ask your IT team or search "ws CVE-2026-45736" on the vendor's site.

CVE-2026-45736 (ws) — CWE-908 / CVSS v3 4.4
Attack vector: remote (network-reachable) / no user interaction
Attack surface: TypedArray
Patched: 8.20.1 — 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-908) exists in ws. Attackers reach the vulnerable code path via TypedArray.

📍 Affected scope

Check the vendor advisory for the affected versions of ws. Attack surface: TypedArray.

🔥 Severity

Severity: Medium (CVSS 4.4/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 8.20.1.

🛡️ 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 request patterns matching this CVE's known IOCs. Run grep -r 'ws' . 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 'ws' . | 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 ws 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
    Apply patch patch 
    Upgrade ws to 8.20.1

    ステージング環境で 8.20.1 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を含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm ws
[{"type":"SEMVER","events":[{"introduced":"8.0.0"},{"fixed":"8.20.1"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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