From 87149c8383f7cdc85cd4780256afc1b5a923bac8 Mon Sep 17 00:00:00 2001
From: x2018 <xkernel.wang@foxmail.com>
Date: Sun, 9 Nov 2025 19:19:13 +0800
Subject: [PATCH] mqtt: properly handle the message which exceeds maxsize

We should goto fail as topic is allocated.

Follow-up to 92fd791

Closes #19417
---
 lib/mqtt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/mqtt.c b/lib/mqtt.c
index bac319e63a..713e4aa02c 100644
--- a/lib/mqtt.c
+++ b/lib/mqtt.c
@@ -613,8 +613,10 @@ static CURLcode mqtt_publish(struct Curl_easy *data)
 
   remaininglength = payloadlen + 2 + topiclen;
   encodelen = mqtt_encode_len(encodedbytes, remaininglength);
-  if(MAX_MQTT_MESSAGE_SIZE - remaininglength - 1 < encodelen)
-    return CURLE_TOO_LARGE;
+  if(MAX_MQTT_MESSAGE_SIZE - remaininglength - 1 < encodelen) {
+    result = CURLE_TOO_LARGE;
+    goto fail;
+  }
 
   /* add the control byte and the encoded remaining length */
   pkt = malloc(remaininglength + 1 + encodelen);