In Node.js including 6.x before 6.17.0 8.x before 8.15.1 10.x before 10.15.2 and 11.x before 11.10.1 an attacker can cause a Denial of Service (DoS) by establishing an HTTP or HTTPS connection in keep-alive mode and by sending headers very slowly. This keeps the connection and associated resources alive for a long period of time. Potential attacks are mitigated by the use of a load balancer or other proxy layer. This vulnerability is an extension of CVE-2018-12121 addressed in November and impacts all active Node.js release lines including 6.x before 6.17.0 8.x before 8.15.1 10.x before 10.15.2 and 11.x before 11.10.1.