Hello, Since the jdk 11u14 we've noticed the issue with two HOST headers in HTTP/2 requests, that was fixed via https://bugs.openjdk.java.net/browse/JDK-8218546 in JDK 12+. One can verify this report by running the test from JDK-8218546. This seems like a good candidate for a backport to JDK 11u. Thanks, Ivan