CVE-2021-32640

What it is

ws is an open source WebSocket client and server library for Node.js. A specially crafted value of the `Sec-Websocket-Protocol` header can be used to significantly slow down a ws server. The vulnerability has been fixed in [email protected] (https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff). In vulnerable versions of ws, the issue can be mitigated by reducing the maximum allowed length of the request headers using the [`--max-http-header-size=size`](https://nodejs.org/api/cli.html#cli_max_http_header_size_size) and/or the [`maxHeaderSize`](https://nodejs.org/api/http.html#http_http_createserver_options_requestlistener) options.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

2.8% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-05-25 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:53 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.8% in the next 30 days (EPSS).
• Severity: 5.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-05-25 19:15 UTC

Last modified

2026-06-17 03:53 UTC

Exploit probability

2.8% · EPSS, next 30 days

Weakness

CWE-400 · Uncontrolled resource consumption

Record status

Modified

Affected

• Ws Project Ws < 6.2.2
• Ws Project Ws < 7.4.6
• Netapp e-series Performance Analyzer

Attack profile CVSS 3.1 · 5.3

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-32640.md and follow it. Check whether this project is affected by CVE-2021-32640. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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