{"id":"CVE-2026-109855","summary":"undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake","details":"undici is an HTTP client library for Node.js. In versions 8.11.0 and 8.11.1, its experimental WebSocket client, which is enabled by default when HTTP/2 is allowed, mishandles a failed WebSocket handshake over HTTP/2: the request is already marked completed, so the abort becomes a no-op and the underlying HTTP/2 stream is left open with no error listener. When a malicious server then destroys the connection, the orphaned stream emits an unhandled error and the Node.js process exits. A remote, unauthenticated server can therefore crash any client that opens a WebSocket to it over HTTP/2, resulting in a denial of service. The issue is fixed in undici 8.11.2, and users should upgrade to 8.11.2 or later. As a workaround, set allowH2 to false to disable HTTP/2 for WebSocket connections, or avoid opening WebSocket connections to untrusted servers.","aliases":["GHSA-qq8j-7v2v-3rwp"],"modified":"2026-10-16T02:47:59.264147762Z","published":"2026-10-15T08:12:51.245Z","database_specific":{"cna_assigner":"openjs","cwe_ids":["CWE-248","CWE-754"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109855.json"},"references":[{"type":"ADVISORY","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109855.json"},{"type":"ADVISORY","url":"https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109855"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nodejs/undici","events":[{"introduced":"6e48f4873a677ed6a13fa3e3571b032f00244bdf"},{"fixed":"7e016ad7e5bd6540170069a9a28b1e633b29664f"}],"database_specific":{"extracted_events":[{"introduced":"8.11.0"},{"fixed":"8.11.2"}],"source":"AFFECTED_FIELD"}}],"versions":["v8.11.1","v8.11.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-109855.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:H"}]}