diff --git a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/AbstractServerHttpRequest.java b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/AbstractServerHttpRequest.java
index b88a3e3b7c6..956e9e391d8 100644
--- a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/AbstractServerHttpRequest.java
+++ b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/AbstractServerHttpRequest.java
@@ -93,8 +93,7 @@ public abstract class AbstractServerHttpRequest implements ServerHttpRequest {
 	@Override
 	public HttpHeaders getHeaders() {
 		if (this.headers == null) {
-			this.headers = new HttpHeaders();
-			initHeaders(this.headers);
+			this.headers = HttpHeaders.readOnlyHttpHeaders(initHeaders());
 		}
 		return this.headers;
 	}
@@ -102,15 +101,13 @@ public abstract class AbstractServerHttpRequest implements ServerHttpRequest {
 	/**
 	 * Initialize the headers from the underlying request. Invoked lazily on the
 	 * first call to {@link #getHeaders()} and then cached.
-	 * @param headers the map to add headers to
 	 */
-	protected abstract void initHeaders(HttpHeaders headers);
+	protected abstract HttpHeaders initHeaders();
 
 	@Override
 	public MultiValueMap<String, HttpCookie> getCookies() {
 		if (this.cookies == null) {
-			this.cookies = new LinkedMultiValueMap<>();
-			initCookies(this.cookies);
+			this.cookies = CollectionUtils.unmodifiableMultiValueMap(initCookies());
 		}
 		return this.cookies;
 	}
@@ -118,8 +115,7 @@ public abstract class AbstractServerHttpRequest implements ServerHttpRequest {
 	/**
 	 * Initialize the cookies from the underlying request. Invoked lazily on the
 	 * first access to cookies via {@link #getHeaders()} and then cached.
-	 * @param cookies the map to add cookies to
 	 */
-	protected abstract void initCookies(MultiValueMap<String, HttpCookie> cookies);
+	protected abstract MultiValueMap<String, HttpCookie> initCookies();
 
 }
diff --git a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ReactorServerHttpRequest.java b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ReactorServerHttpRequest.java
index 2348d995c5d..5183fca307e 100644
--- a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ReactorServerHttpRequest.java
+++ b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ReactorServerHttpRequest.java
@@ -29,6 +29,7 @@ import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.util.Assert;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
 /**
@@ -66,20 +67,24 @@ public class ReactorServerHttpRequest extends AbstractServerHttpRequest {
 	}
 
 	@Override
-	protected void initHeaders(HttpHeaders headers) {
+	protected HttpHeaders initHeaders() {
+		HttpHeaders headers = new HttpHeaders();
 		for (String name : this.channel.headers().names()) {
 			headers.put(name, this.channel.headers().getAll(name));
 		}
+		return headers;
 	}
 
 	@Override
-	protected void initCookies(MultiValueMap<String, HttpCookie> cookies) {
+	protected MultiValueMap<String, HttpCookie> initCookies() {
+		MultiValueMap<String, HttpCookie> cookies = new LinkedMultiValueMap<>();
 		for (CharSequence name : this.channel.cookies().keySet()) {
 			for (Cookie cookie : this.channel.cookies().get(name)) {
 				HttpCookie httpCookie = new HttpCookie(name.toString(), cookie.value());
 				cookies.add(name.toString(), httpCookie);
 			}
 		}
+		return cookies;
 	}
 
 	@Override
diff --git a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/RxNettyServerHttpRequest.java b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/RxNettyServerHttpRequest.java
index e3b15620054..dab7c23f837 100644
--- a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/RxNettyServerHttpRequest.java
+++ b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/RxNettyServerHttpRequest.java
@@ -32,6 +32,7 @@ import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.util.Assert;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
 /**
@@ -70,20 +71,24 @@ public class RxNettyServerHttpRequest extends AbstractServerHttpRequest {
 	}
 
 	@Override
-	protected void initHeaders(HttpHeaders headers) {
+	protected HttpHeaders initHeaders() {
+		HttpHeaders headers = new HttpHeaders();
 		for (String name : this.request.getHeaderNames()) {
 			headers.put(name, this.request.getAllHeaderValues(name));
 		}
+		return headers;
 	}
 
 	@Override
-	protected void initCookies(MultiValueMap<String, HttpCookie> cookies) {
+	protected MultiValueMap<String, HttpCookie> initCookies() {
+		MultiValueMap<String, HttpCookie> cookies = new LinkedMultiValueMap<>();
 		for (String name : this.request.getCookies().keySet()) {
 			for (Cookie cookie : this.request.getCookies().get(name)) {
 				HttpCookie httpCookie = new HttpCookie(name, cookie.value());
 				cookies.add(name, httpCookie);
 			}
 		}
+		return cookies;
 	}
 
 	@Override
diff --git a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ServletServerHttpRequest.java b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ServletServerHttpRequest.java
index 952a93cc7c5..9cd8586e7d0 100644
--- a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ServletServerHttpRequest.java
+++ b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/ServletServerHttpRequest.java
@@ -24,8 +24,6 @@ import java.util.Map;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletRequest;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 
@@ -36,6 +34,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedCaseInsensitiveMap;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.util.StringUtils;
 
@@ -46,8 +45,6 @@ import org.springframework.util.StringUtils;
  */
 public class ServletServerHttpRequest extends AbstractServerHttpRequest {
 
-	private static final Log logger = LogFactory.getLog(ServletServerHttpRequest.class);
-
 	private final HttpServletRequest request;
 
 	private final Flux<DataBuffer> requestBodyPublisher;
@@ -81,7 +78,8 @@ public class ServletServerHttpRequest extends AbstractServerHttpRequest {
 	}
 
 	@Override
-	protected void initHeaders(HttpHeaders headers) {
+	protected HttpHeaders initHeaders() {
+		HttpHeaders headers = new HttpHeaders();
 		for (Enumeration<?> names = getServletRequest().getHeaderNames(); names.hasMoreElements(); ) {
 			String name = (String) names.nextElement();
 			for (Enumeration<?> values = getServletRequest().getHeaders(name); values.hasMoreElements(); ) {
@@ -112,10 +110,12 @@ public class ServletServerHttpRequest extends AbstractServerHttpRequest {
 				headers.setContentLength(contentLength);
 			}
 		}
+		return headers;
 	}
 
 	@Override
-	protected void initCookies(MultiValueMap<String, HttpCookie> httpCookies) {
+	protected MultiValueMap<String, HttpCookie> initCookies() {
+		MultiValueMap<String, HttpCookie> httpCookies = new LinkedMultiValueMap<>();
 		Cookie[] cookies = this.request.getCookies();
 		if (cookies != null) {
 			for (Cookie cookie : cookies) {
@@ -124,6 +124,7 @@ public class ServletServerHttpRequest extends AbstractServerHttpRequest {
 				httpCookies.add(name, httpCookie);
 			}
 		}
+		return httpCookies;
 	}
 
 	@Override
diff --git a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java
index cebcc776ed2..51ef11d4453 100644
--- a/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java
+++ b/spring-web-reactive/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java
@@ -30,6 +30,7 @@ import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.util.Assert;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
 /**
@@ -70,19 +71,23 @@ public class UndertowServerHttpRequest extends AbstractServerHttpRequest {
 	}
 
 	@Override
-	protected void initHeaders(HttpHeaders headers) {
+	protected HttpHeaders initHeaders() {
+		HttpHeaders headers = new HttpHeaders();
 		for (HeaderValues values : this.getUndertowExchange().getRequestHeaders()) {
 			headers.put(values.getHeaderName().toString(), values);
 		}
+		return headers;
 	}
 
 	@Override
-	protected void initCookies(MultiValueMap<String, HttpCookie> cookies) {
+	protected MultiValueMap<String, HttpCookie> initCookies() {
+		MultiValueMap<String, HttpCookie> cookies = new LinkedMultiValueMap<>();
 		for (String name : this.exchange.getRequestCookies().keySet()) {
 			Cookie cookie = this.exchange.getRequestCookies().get(name);
 			HttpCookie httpCookie = new HttpCookie(name, cookie.getValue());
 			cookies.add(name, httpCookie);
 		}
+		return cookies;
 	}
 
 	@Override