{"schema":"threatline.record/2","record":{"id":"CVE-2026-109855","aliases":["GHSA-qq8j-7v2v-3rwp"],"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.","categories":["Unclassified"],"product":"undici","vendor":"undici","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-109855","source_modified_at":"2026-10-15T14:22:28.644Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"undici","vendor":"undici","versions":[{"versionType":"semver","status":"affected","version":"8.11.0","lessThan":"8.11.2"},{"versionType":"semver","status":"unaffected","version":"8.11.2"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-109855","source_modified_at":"2026-10-15T14:22:28.644Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"undici","ecosystem":null},"version":"8.11.2","basis":"first unaffected version stated in the CVE record"}],"cvss":7.5,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00278,"percentile":0.19255,"score_date":"2026-10-23"},"published_at":"2026-10-15T08:12:51.245Z","modified_at":"2026-10-15T14:22:28.644Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-109855","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-15T14:22:28.644Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-109855","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp"},{"source":"CVE List","url":"https://cna.openjsf.org/security-advisories.html"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"yes","technical_impact":"partial","assessed_at":"2026-10-15T14:21:59.498708Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-15T14:22:28.644Z","content_hash":"c3c56f7ae50ce80da7f136d51e33796d125307e5573544d708bdfc7161090bc1"}}