{"id":"CVE-2026-109855","revision":"1cf958cf0f7d49ca9c77bfe45003c02f","records":[{"revision":"1cf958cf0f7d49ca9c77bfe45003c02f","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-109855","aliases":[],"title":"undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake","description":"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.","state":0,"publishedAt":"2026-10-15T08:12:51.245+00:00","modifiedAt":"2026-10-15T14:22:28.644+00:00","affected":[{"ecosystem":"Vendor product","name":"undici","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"undici\",\n                    \"product\": \"undici\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"versions\": [\n                        {\n                            \"versionType\": \"semver\",\n                            \"status\": \"affected\",\n                            \"version\": \"8.11.0\",\n                            \"lessThan\": \"8.11.2\"\n                        },\n                        {\n                            \"versionType\": \"semver\",\n                            \"status\": \"unaffected\",\n                            \"version\": \"8.11.2\"\n                        }\n                    ],\n                    \"packageURL\": \"pkg:npm/undici\"\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp","https://cna.openjsf.org/security-advisories.html"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-109855","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-109855","identifiers":["CVE-2026-109855"]},"retained":false,"historicalAffected":[]}],"coverage":[]}