diff --git a/x-pack/qa/evil-tests/src/test/java/org/elasticsearch/xpack/security/authc/kerberos/SimpleKdcLdapServer.java b/x-pack/qa/evil-tests/src/test/java/org/elasticsearch/xpack/security/authc/kerberos/SimpleKdcLdapServer.java
index 13601d2fe202f..8888ce33be57f 100644
--- a/x-pack/qa/evil-tests/src/test/java/org/elasticsearch/xpack/security/authc/kerberos/SimpleKdcLdapServer.java
+++ b/x-pack/qa/evil-tests/src/test/java/org/elasticsearch/xpack/security/authc/kerberos/SimpleKdcLdapServer.java
@@ -13,7 +13,6 @@
 import org.apache.kerby.kerberos.kerb.client.KrbConfig;
 import org.apache.kerby.kerberos.kerb.server.KdcConfigKey;
 import org.apache.kerby.kerberos.kerb.server.SimpleKdcServer;
-import org.apache.kerby.util.NetworkUtil;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ExceptionsHelper;
@@ -22,6 +21,9 @@
 import org.elasticsearch.test.ESTestCase;
 
 import java.io.IOException;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.net.ServerSocket;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -31,6 +33,8 @@
 import java.util.Locale;
 import java.util.concurrent.TimeUnit;
 
+import javax.net.ServerSocketFactory;
+
 /**
  * Utility wrapper around Apache {@link SimpleKdcServer} backed by Unboundid
  * {@link InMemoryDirectoryServer}.<br>
@@ -127,14 +131,14 @@ private void prepareKdcServerAndStart() throws Exception {
         simpleKdc.setWorkDir(workDir.toFile());
         simpleKdc.setKdcHost(host);
         simpleKdc.setKdcRealm(realm);
-        if (kdcPort == 0) {
-            kdcPort = NetworkUtil.getServerPort();
-        }
         if (transport != null) {
-            if (transport.trim().equals("TCP")) {
+            if (kdcPort == 0) {
+                kdcPort = getServerPort(transport);
+            }
+            if (transport.trim().equalsIgnoreCase("TCP")) {
                 simpleKdc.setKdcTcpPort(kdcPort);
                 simpleKdc.setAllowUdp(false);
-            } else if (transport.trim().equals("UDP")) {
+            } else if (transport.trim().equalsIgnoreCase("UDP")) {
                 simpleKdc.setKdcUdpPort(kdcPort);
                 simpleKdc.setAllowTcp(false);
             } else {
@@ -221,4 +225,21 @@ public Void run() throws Exception {
         logger.info("SimpleKdcServer stoppped.");
     }
 
+    private static int getServerPort(String transport) {
+        if (transport != null && transport.trim().equalsIgnoreCase("TCP")) {
+            try (ServerSocket serverSocket = ServerSocketFactory.getDefault().createServerSocket(0, 1,
+                    InetAddress.getByName("127.0.0.1"))) {
+                return serverSocket.getLocalPort();
+            } catch (Exception ex) {
+                throw new RuntimeException("Failed to get a TCP server socket point");
+            }
+        } else if (transport != null && transport.trim().equalsIgnoreCase("UDP")) {
+            try (DatagramSocket socket = new DatagramSocket(0, InetAddress.getByName("127.0.0.1"))) {
+                return socket.getLocalPort();
+            } catch (Exception ex) {
+                throw new RuntimeException("Failed to get a UDP server socket point");
+            }
+        }
+        throw new IllegalArgumentException("Invalid transport: " + transport);
+    }
 }