{"id":"CVE-2021-32640","aliases":["GHSA-6fc8-4gx4-v693"],"url":"https://o3.security/vulnerability/CVE-2021-32640","summary":"ReDoS in Sec-Websocket-Protocol header","details":"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 ws@7.4.6 (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.","published":"2021-05-25T19:15:07.767Z","modified":"2026-07-09T12:20:09.027755Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"npm","name":"ws","fixedVersion":"7.4.6"},{"ecosystem":"npm","name":"ws","fixedVersion":"6.2.2"},{"ecosystem":"npm","name":"ws","fixedVersion":"5.2.3"}],"fix":{"url":"https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff","label":"websockets/ws@00c425e"},"references":[{"type":"WEB","url":"https://lists.apache.org/thread.html/rdfa7b6253c4d6271e31566ecd5f30b7ce1b8fb2c89d52b8c4e0f4e30%40%3Ccommits.tinkerpop.apache.org%3E"},{"type":"ADVISORY","url":"https://security.netapp.com/advisory/ntap-20210706-0005/"},{"type":"FIX","url":"https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff"},{"type":"FIX","url":"https://github.com/websockets/ws/security/advisories/GHSA-6fc8-4gx4-v693"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T12:20:09.027755Z"}}