diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java
index 29810935a6c..c68b5135887 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -654,11 +654,14 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	@Override
 	public String getServerName() {
-		String host = getHeader(HttpHeaders.HOST);
+		String rawHostHeader = getHeader(HttpHeaders.HOST);
+		String host = rawHostHeader;
 		if (host != null) {
 			host = host.trim();
 			if (host.startsWith("[")) {
-				host = host.substring(1, host.indexOf(']'));
+				int indexOfClosingBracket = host.indexOf(']');
+				Assert.state(indexOfClosingBracket > -1, () -> "Invalid Host header: " + rawHostHeader);
+				host = host.substring(0, indexOfClosingBracket + 1);
 			}
 			else if (host.contains(":")) {
 				host = host.substring(0, host.indexOf(':'));
@@ -676,12 +679,15 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	@Override
 	public int getServerPort() {
-		String host = getHeader(HttpHeaders.HOST);
+		String rawHostHeader = getHeader(HttpHeaders.HOST);
+		String host = rawHostHeader;
 		if (host != null) {
 			host = host.trim();
 			int idx;
 			if (host.startsWith("[")) {
-				idx = host.indexOf(':', host.indexOf(']'));
+				int indexOfClosingBracket = host.indexOf(']');
+				Assert.state(indexOfClosingBracket > -1, () -> "Invalid Host header: " + rawHostHeader);
+				idx = host.indexOf(':', indexOfClosingBracket);
 			}
 			else {
 				idx = host.indexOf(':');
diff --git a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletRequestTests.java b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletRequestTests.java
index 502a807592c..15b1c43e085 100644
--- a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletRequestTests.java
+++ b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletRequestTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.mock.web;
 
 import java.io.IOException;
+import java.net.URL;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -37,6 +38,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.util.FileCopyUtils;
 import org.springframework.util.StreamUtils;
 
+import static org.hamcrest.CoreMatchers.startsWith;
 import static org.junit.Assert.*;
 
 /**
@@ -347,16 +349,23 @@ public class MockHttpServletRequestTests {
 
 	@Test
 	public void getServerNameViaHostHeaderAsIpv6AddressWithoutPort() {
-		String ipv6Address = "[2001:db8:0:1]";
-		request.addHeader(HOST, ipv6Address);
-		assertEquals("2001:db8:0:1", request.getServerName());
+		String host = "[2001:db8:0:1]";
+		request.addHeader(HOST, host);
+		assertEquals(host, request.getServerName());
 	}
 
 	@Test
 	public void getServerNameViaHostHeaderAsIpv6AddressWithPort() {
-		String ipv6Address = "[2001:db8:0:1]:8081";
-		request.addHeader(HOST, ipv6Address);
-		assertEquals("2001:db8:0:1", request.getServerName());
+		request.addHeader(HOST, "[2001:db8:0:1]:8081");
+		assertEquals("[2001:db8:0:1]", request.getServerName());
+	}
+
+	@Test
+	public void getServerNameWithInvalidIpv6AddressViaHostHeader() {
+		request.addHeader(HOST, "[::ffff:abcd:abcd"); // missing closing bracket
+		exception.expect(IllegalStateException.class);
+		exception.expectMessage(startsWith("Invalid Host header: "));
+		request.getServerName();
 	}
 
 	@Test
@@ -370,6 +379,22 @@ public class MockHttpServletRequestTests {
 		assertEquals(8080, request.getServerPort());
 	}
 
+	@Test
+	public void getServerPortWithInvalidIpv6AddressViaHostHeader() {
+		request.addHeader(HOST, "[::ffff:abcd:abcd:8080"); // missing closing bracket
+		exception.expect(IllegalStateException.class);
+		exception.expectMessage(startsWith("Invalid Host header: "));
+		request.getServerPort();
+	}
+
+	@Test
+	public void getServerPortWithIpv6AddressAndInvalidPortViaHostHeader() {
+		request.addHeader(HOST, "[::ffff:abcd:abcd]:bogus"); // "bogus" is not a port number
+		exception.expect(NumberFormatException.class);
+		exception.expectMessage("bogus");
+		request.getServerPort();
+	}
+
 	@Test
 	public void getServerPortViaHostHeaderAsIpv6AddressWithoutPort() {
 		String testServer = "[2001:db8:0:1]";
@@ -434,6 +459,43 @@ public class MockHttpServletRequestTests {
 		assertEquals("http://" + testServer, requestURL.toString());
 	}
 
+	@Test
+	public void getRequestURLWithIpv6AddressViaServerNameWithoutPort() throws Exception {
+		request.setServerName("[::ffff:abcd:abcd]");
+		URL url = new java.net.URL(request.getRequestURL().toString());
+		assertEquals("http://[::ffff:abcd:abcd]", url.toString());
+	}
+
+	@Test
+	public void getRequestURLWithIpv6AddressViaServerNameWithPort() throws Exception {
+		request.setServerName("[::ffff:abcd:abcd]");
+		request.setServerPort(9999);
+		URL url = new java.net.URL(request.getRequestURL().toString());
+		assertEquals("http://[::ffff:abcd:abcd]:9999", url.toString());
+	}
+
+	@Test
+	public void getRequestURLWithInvalidIpv6AddressViaHostHeader() {
+		request.addHeader(HOST, "[::ffff:abcd:abcd"); // missing closing bracket
+		exception.expect(IllegalStateException.class);
+		exception.expectMessage(startsWith("Invalid Host header: "));
+		request.getRequestURL();
+	}
+
+	@Test
+	public void getRequestURLWithIpv6AddressViaHostHeaderWithoutPort() throws Exception {
+		request.addHeader(HOST, "[::ffff:abcd:abcd]");
+		URL url = new java.net.URL(request.getRequestURL().toString());
+		assertEquals("http://[::ffff:abcd:abcd]", url.toString());
+	}
+
+	@Test
+	public void getRequestURLWithIpv6AddressViaHostHeaderWithPort() throws Exception {
+		request.addHeader(HOST, "[::ffff:abcd:abcd]:9999");
+		URL url = new java.net.URL(request.getRequestURL().toString());
+		assertEquals("http://[::ffff:abcd:abcd]:9999", url.toString());
+	}
+
 	@Test
 	public void getRequestURLWithNullRequestUri() {
 		request.setRequestURI(null);
diff --git a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletRequest.java b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletRequest.java
index bdfb905190d..bfffe31ac4a 100644
--- a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletRequest.java
+++ b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletRequest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -654,11 +654,14 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	@Override
 	public String getServerName() {
-		String host = getHeader(HttpHeaders.HOST);
+		String rawHostHeader = getHeader(HttpHeaders.HOST);
+		String host = rawHostHeader;
 		if (host != null) {
 			host = host.trim();
 			if (host.startsWith("[")) {
-				host = host.substring(1, host.indexOf(']'));
+				int indexOfClosingBracket = host.indexOf(']');
+				Assert.state(indexOfClosingBracket > -1, () -> "Invalid Host header: " + rawHostHeader);
+				host = host.substring(0, indexOfClosingBracket + 1);
 			}
 			else if (host.contains(":")) {
 				host = host.substring(0, host.indexOf(':'));
@@ -676,12 +679,15 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	@Override
 	public int getServerPort() {
-		String host = getHeader(HttpHeaders.HOST);
+		String rawHostHeader = getHeader(HttpHeaders.HOST);
+		String host = rawHostHeader;
 		if (host != null) {
 			host = host.trim();
 			int idx;
 			if (host.startsWith("[")) {
-				idx = host.indexOf(':', host.indexOf(']'));
+				int indexOfClosingBracket = host.indexOf(']');
+				Assert.state(indexOfClosingBracket > -1, () -> "Invalid Host header: " + rawHostHeader);
+				idx = host.indexOf(':', indexOfClosingBracket);
 			}
 			else {
 				idx = host.indexOf(':');