From 39a746d30f82bf63b2906ecba82303cf311b9fc2 Mon Sep 17 00:00:00 2001
From: cuitianhao <54015884+tianhaocui@users.noreply.github.com>
Date: Sun, 19 Apr 2026 17:55:53 +0800
Subject: [PATCH] Set host header consistently in STOMP relay CONNECT frames

StompBrokerRelayMessageHandler only set the host header in CONNECT
frames when virtualHost was explicitly configured. Per STOMP 1.2, the
host header is required on CONNECT frames.

Fall back to relayHost (the TCP connection target) when virtualHost is
not configured, ensuring the host header is always present in both
system session and client session CONNECT frames.

Closes gh-36673

Signed-off-by: cuitianhao <54015884+tianhaocui@users.noreply.github.com>
---
 .../simp/stomp/StompBrokerRelayMessageHandler.java       | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompBrokerRelayMessageHandler.java b/spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompBrokerRelayMessageHandler.java
index cab92b50ac8..6c5aeb5f17e 100644
--- a/spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompBrokerRelayMessageHandler.java
+++ b/spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompBrokerRelayMessageHandler.java
@@ -456,10 +456,7 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 		accessor.setLogin(this.systemLogin);
 		accessor.setPasscode(this.systemPasscode);
 		accessor.setHeartbeat(this.systemHeartbeatSendInterval, this.systemHeartbeatReceiveInterval);
-		String virtualHost = getVirtualHost();
-		if (virtualHost != null) {
-			accessor.setHost(virtualHost);
-		}
+		accessor.setHost(getVirtualHost() != null ? getVirtualHost() : getRelayHost());
 		accessor.setSessionId(SYSTEM_SESSION_ID);
 		if (logger.isDebugEnabled()) {
 			logger.debug("Forwarding " + accessor.getShortLogMessage(EMPTY_PAYLOAD));
@@ -582,9 +579,7 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 			stompHeaderAccessor = (stompHeaderAccessor.isMutable() ? stompHeaderAccessor : StompHeaderAccessor.wrap(message));
 			stompHeaderAccessor.setLogin(this.clientLogin);
 			stompHeaderAccessor.setPasscode(this.clientPasscode);
-			if (getVirtualHost() != null) {
-				stompHeaderAccessor.setHost(getVirtualHost());
-			}
+			stompHeaderAccessor.setHost(getVirtualHost() != null ? getVirtualHost() : getRelayHost());
 			RelayConnectionHandler handler = new RelayConnectionHandler(sessionId, stompHeaderAccessor);
 			this.connectionHandlers.put(sessionId, handler);
 			this.stats.incrementConnectCount();