In Eclipse Vert.x version 3.0 to 3.5.1, the HttpServer response headers and HttpClient request headers do not filter carriage return and line feed characters from the header value. This allow unfiltered values to inject a new header in the client request or server response.
https://www.compass-security.com/fileadmin/Datein/Research/Advisories/CSNC-2018-021_vertx.txt
https://github.com/eclipse/vert.x/issues/2470
https://github.com/eclipse/vert.x/commit/1bb6445226c39a95e7d07ce3caaf56828e8aab72
https://bugzilla.redhat.com/show_bug.cgi?id=1591072
https://bugs.eclipse.org/bugs/show_bug.cgi?id=536038