diff --git a/spring-boot-project/spring-boot-dependencies/pom.xml b/spring-boot-project/spring-boot-dependencies/pom.xml
index 5f19067146d..43ff32820be 100644
--- a/spring-boot-project/spring-boot-dependencies/pom.xml
+++ b/spring-boot-project/spring-boot-dependencies/pom.xml
@@ -203,7 +203,7 @@
 		<thymeleaf-extras-java8time.version>3.0.4.RELEASE</thymeleaf-extras-java8time.version>
 		<tomcat.version>9.0.21</tomcat.version>
 		<unboundid-ldapsdk.version>4.0.11</unboundid-ldapsdk.version>
-		<undertow.version>2.0.21.Final</undertow.version>
+		<undertow.version>2.0.22.Final</undertow.version>
 		<webjars-hal-browser.version>3325375</webjars-hal-browser.version>
 		<webjars-locator-core.version>0.37</webjars-locator-core.version>
 		<woodstox.version>5.0.3</woodstox.version>
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java
index a87fe5bb064..fe4d83285b6 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactory.java
@@ -27,7 +27,10 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.EventListener;
 import java.util.LinkedHashSet;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
+import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
 
@@ -57,6 +60,7 @@ import io.undertow.servlet.api.ListenerInfo;
 import io.undertow.servlet.api.MimeMapping;
 import io.undertow.servlet.api.ServletContainerInitializerInfo;
 import io.undertow.servlet.api.ServletStackTraces;
+import io.undertow.servlet.core.DeploymentImpl;
 import io.undertow.servlet.handlers.DefaultServlet;
 import io.undertow.servlet.util.ImmediateInstanceFactory;
 import org.xnio.OptionMap;
@@ -282,6 +286,9 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 		addLocaleMappings(deployment);
 		DeploymentManager manager = Servlets.newContainer().addDeployment(deployment);
 		manager.deploy();
+		if (manager.getDeployment() instanceof DeploymentImpl) {
+			removeSuperfluousMimeMappings((DeploymentImpl) manager.getDeployment(), deployment);
+		}
 		SessionManager sessionManager = manager.getDeployment().getSessionManager();
 		Duration timeoutDuration = getSession().getTimeout();
 		int sessionTimeout = (isZeroOrLess(timeoutDuration) ? -1 : (int) timeoutDuration.getSeconds());
@@ -416,6 +423,16 @@ public class UndertowServletWebServerFactory extends AbstractServletWebServerFac
 		}
 	}
 
+	private void removeSuperfluousMimeMappings(DeploymentImpl deployment, DeploymentInfo deploymentInfo) {
+		// DeploymentManagerImpl will always add MimeMappings.DEFAULT_MIME_MAPPINGS
+		// but we only want ours
+		Map<String, String> mappings = new HashMap<>();
+		for (MimeMapping mapping : deploymentInfo.getMimeMappings()) {
+			mappings.put(mapping.getExtension().toLowerCase(Locale.ENGLISH), mapping.getMimeType());
+		}
+		deployment.setMimeExtensionMappings(mappings);
+	}
+
 	/**
 	 * Factory method called to create the {@link UndertowServletWebServer}. Subclasses
 	 * can override this method to return a different {@link UndertowServletWebServer} or
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java
index c7df2f26952..2023d32fd75 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java
@@ -22,11 +22,8 @@ import java.net.SocketException;
 import java.net.URISyntaxException;
 import java.nio.charset.Charset;
 import java.util.Arrays;
-import java.util.Collection;
-import java.util.HashSet;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
 
 import javax.net.ssl.SSLException;
@@ -42,7 +39,6 @@ import org.mockito.InOrder;
 
 import org.springframework.boot.testsupport.web.servlet.ExampleServlet;
 import org.springframework.boot.web.server.ErrorPage;
-import org.springframework.boot.web.server.MimeMappings.Mapping;
 import org.springframework.boot.web.server.PortInUseException;
 import org.springframework.boot.web.servlet.ServletRegistrationBean;
 import org.springframework.boot.web.servlet.server.AbstractServletWebServerFactory;
@@ -261,15 +257,6 @@ class UndertowServletWebServerFactoryTests extends AbstractServletWebServerFacto
 				.getMimeExtensionMappings();
 	}
 
-	@Override
-	protected Collection<Mapping> getExpectedMimeMappings() {
-		// Unlike Tomcat and Jetty, Undertow performs a case-sensitive match on file
-		// extension so it has a mapping for "z" and "Z".
-		Set<Mapping> expectedMappings = new HashSet<>(super.getExpectedMimeMappings());
-		expectedMappings.add(new Mapping("Z", "application/x-compress"));
-		return expectedMappings;
-	}
-
 	@Override
 	protected Charset getCharset(Locale locale) {
 		DeploymentInfo info = ((UndertowServletWebServer) this.webServer).getDeploymentManager().getDeployment()
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactoryTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactoryTests.java
index 2301c36d81f..cabc48689db 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactoryTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactoryTests.java
@@ -779,7 +779,7 @@ public abstract class AbstractServletWebServerFactoryTests {
 		AbstractServletWebServerFactory factory = getFactory();
 		this.webServer = factory.getWebServer();
 		Map<String, String> configuredMimeMappings = getActualMimeMappings();
-		Collection<MimeMappings.Mapping> expectedMimeMappings = getExpectedMimeMappings();
+		Collection<MimeMappings.Mapping> expectedMimeMappings = MimeMappings.DEFAULT.getAll();
 		configuredMimeMappings.forEach(
 				(key, value) -> assertThat(expectedMimeMappings).contains(new MimeMappings.Mapping(key, value)));
 		for (MimeMappings.Mapping mapping : expectedMimeMappings) {
@@ -1016,10 +1016,6 @@ public abstract class AbstractServletWebServerFactoryTests {
 
 	protected abstract Map<String, String> getActualMimeMappings();
 
-	protected Collection<MimeMappings.Mapping> getExpectedMimeMappings() {
-		return MimeMappings.DEFAULT.getAll();
-	}
-
 	protected abstract Charset getCharset(Locale locale);
 
 	private void addTestTxtFile(AbstractServletWebServerFactory factory) throws IOException {