{"cve":"CVE-2026-19534","nvd":{"published":"2026-09-04T18:17:51.647","modified":"2026-09-16T20:41:08.750","status":"Analyzed","description":"undici's WebSocket client crashes the whole Node.js process during the opening handshake when a server responds with a subprotocol that the client never requested. A default WebSocket connection sends no subprotocol, but if the server's 101 response includes a Sec-WebSocket-Protocol header, undici dereferences a null value while checking it against the requested list and throws an uncaught TypeError. Because that code runs inside a microtask with no surrounding error handling, the exception propagates and terminates the process under Node's default behavior, instead of gracefully failing the connection as required by the WebSocket protocol. Any application that opens a WebSocket to an attacker-controlled or compromised server, or over a plaintext connection subject to a machine-in-the-middle, can be crashed remotely without authentication in the default configuration. This affects undici versions from 6.7.0 up to 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.","cvss_v4":null,"cvss_v3":{"version":"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},"cwes":["CWE-248","CWE-252"],"references":["https://cna.openjsf.org/security-advisories.html","https://github.com/nodejs/undici/security/advisories/GHSA-rfgv-xxqx-mfg5"],"products":["nodejs:undici"],"source":"nvd","synced_at":"2026-10-19T22:52:03.409947763+00:00"},"epss":{"cve":"CVE-2026-19534","score":0.00394,"percentile":0.33598,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-rfgv-xxqx-mfg5","url":"https://osv.dev/vulnerability/GHSA-rfgv-xxqx-mfg5","summary":"undici vulnerable to Denial of Service via unrequested WebSocket subprotocol","modified":"2026-09-29T18:30:41.167602268Z","packages":[{"ecosystem":"npm","name":"undici","purl":"pkg:npm/undici","ranges":[">=6.7.0 <6.28.1"],"fixed":["6.28.1"]},{"ecosystem":"npm","name":"undici","purl":"pkg:npm/undici","ranges":[">=7.0.0 <7.29.1"],"fixed":["7.29.1"]},{"ecosystem":"npm","name":"undici","purl":"pkg:npm/undici","ranges":[">=8.0.0 <8.10.2"],"fixed":["8.10.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}