{"id":"GHSA-qq8j-7v2v-3rwp","revision":"d5ae20a622e54ed5b7b7fd90db54a14b","records":[{"revision":"d5ae20a622e54ed5b7b7fd90db54a14b","observedAt":"2026-10-27T16:44:03.037+00:00","statement":{"source":"osv","id":"GHSA-qq8j-7v2v-3rwp","aliases":["CVE-2026-109855"],"title":"undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake","description":"### Impact\n\nundici's experimental WebSocket client (enabled by default via `allowH2: true`) crashes the Node.js process when it connects to a malicious server over HTTP/2. If the server answers the WebSocket upgrade with a response that fails handshake validation, undici aborts the request, but the abort is a no-op because the request is already marked completed, so the underlying `ClientHttp2Stream` is left open with no error listener. When the server then destroys the connection, the orphaned stream emits an unhandled `error` and the process exits. A remote, unauthenticated server can therefore deny service to any client that opens a WebSocket to it over HTTP/2. undici 8.11.0 and 8.11.1 are affected; the regression was introduced in 8.11.0.\n\n### Patches\n\nUpgrade to `8.11.2`.\n\n### Workarounds\n\nSet `allowH2: false` to disable HTTP/2 for WebSocket connections, or avoid opening WebSocket connections to untrusted servers, until upgrading.","state":0,"publishedAt":"2026-10-27T16:09:45+00:00","modifiedAt":"2026-10-27T16:15:05.3463355+00:00","affected":[{"ecosystem":"npm","name":"undici","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"8.11.0"},{"kind":"fixed","version":"8.11.2"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp","https://nvd.nist.gov/vuln/detail/CVE-2026-109855","https://github.com/nodejs/undici/pull/5873","https://github.com/nodejs/undici/commit/dd28c5c55f4a25f7c441fd4365b1191f96c3b8bf","https://cna.openjsf.org/security-advisories.html","https://github.com/nodejs/undici","https://github.com/nodejs/undici/releases/tag/v8.11.2"],"sourceUrl":"https://github.com/advisories/GHSA-qq8j-7v2v-3rwp","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-qq8j-7v2v-3rwp","identifiers":["GHSA-qq8j-7v2v-3rwp","CVE-2026-109855"]},"retained":false,"historicalAffected":[]}],"coverage":[]}