diff --git a/spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java b/spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java
index f66b9ccbdc..ff33f1bc2d 100644
--- a/spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java
+++ b/spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java
@@ -146,6 +146,7 @@ public class UndertowServerHttpRequest extends AbstractServerHttpRequest {
 				this.pooledByteBuffer = this.byteBufferPool.allocate();
 			}
 			ByteBuffer byteBuffer = this.pooledByteBuffer.getBuffer();
+			byteBuffer.clear();
 			int read = this.channel.read(byteBuffer);
 			if (logger.isTraceEnabled()) {
 				logger.trace("read:" + read);