In Ruby before 2.2.10 2.3.x before 2.3.7 2.4.x before 2.4.4 2.5.x before 2.5.1 and 2.6.0-preview1 an attacker can pass a large HTTP request with a crafted header to WEBrick server or a crafted body to WEBrick server/handler and cause a denial of service (memory consumption).