{"id":"GHSA-6fc8-4gx4-v693","summary":"ReDoS in Sec-Websocket-Protocol header","details":"### Impact\n\nA specially crafted value of the `Sec-Websocket-Protocol` header can be used to significantly slow down a ws server.\n\n### Proof of concept\n\n```js\nfor (const length of [1000, 2000, 4000, 8000, 16000, 32000]) {\n  const value = 'b' + ' '.repeat(length) + 'x';\n  const start = process.hrtime.bigint();\n\n  value.trim().split(/ *, */);\n\n  const end = process.hrtime.bigint();\n\n  console.log('length = %d, time = %f ns', length, end - start);\n}\n```\n\n### Patches\n\nThe vulnerability was fixed in ws@7.4.6 (https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff) and backported to ws@6.2.2 (https://github.com/websockets/ws/commit/78c676d2a1acefbc05292e9f7ea0a9457704bf1b) and ws@5.2.3 (https://github.com/websockets/ws/commit/76d47c1479002022a3e4357b3c9f0e23a68d4cd2).\n\n### Workarounds\n\nIn 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.\n\n### Credits\n\nThe vulnerability was responsibly disclosed along with a fix in private by [Robert McLaughlin](https://github.com/robmcl4) from University of California, Santa Barbara.\n","aliases":["CVE-2021-32640"],"modified":"2026-05-07T05:02:25.801182147Z","published":"2021-05-28T19:19:03Z","database_specific":{"cwe_ids":["CWE-345","CWE-400"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2021-05-28T18:18:04Z","nvd_published_at":"2021-05-25T19:15:00Z"},"references":[{"type":"WEB","url":"https://github.com/websockets/ws/security/advisories/GHSA-6fc8-4gx4-v693"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-32640"},{"type":"WEB","url":"https://github.com/websockets/ws/issues/1895"},{"type":"WEB","url":"https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff"},{"type":"PACKAGE","url":"https://github.com/websockets/ws"},{"type":"WEB","url":"https://lists.apache.org/thread.html/rdfa7b6253c4d6271e31566ecd5f30b7ce1b8fb2c89d52b8c4e0f4e30@%3Ccommits.tinkerpop.apache.org%3E"},{"type":"WEB","url":"https://security.netapp.com/advisory/ntap-20210706-0005"}],"affected":[{"package":{"name":"ws","ecosystem":"npm","purl":"pkg:npm/ws"},"ranges":[{"type":"SEMVER","events":[{"introduced":"7.0.0"},{"fixed":"7.4.6"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/05/GHSA-6fc8-4gx4-v693/GHSA-6fc8-4gx4-v693.json"}},{"package":{"name":"ws","ecosystem":"npm","purl":"pkg:npm/ws"},"ranges":[{"type":"SEMVER","events":[{"introduced":"6.0.0"},{"fixed":"6.2.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/05/GHSA-6fc8-4gx4-v693/GHSA-6fc8-4gx4-v693.json"}},{"package":{"name":"ws","ecosystem":"npm","purl":"pkg:npm/ws"},"ranges":[{"type":"SEMVER","events":[{"introduced":"5.0.0"},{"fixed":"5.2.3"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/05/GHSA-6fc8-4gx4-v693/GHSA-6fc8-4gx4-v693.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}