From 87da3e845be515ddbb1542d0d17e66e843610d3a Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Tue, 29 Mar 2022 08:43:13 +0200
Subject: [PATCH] mqtt: better handling of TCP disconnect mid-message

Reported-by: Jenny Heino
Bug: https://hackerone.com/reports/1521610
Closes #8644
---
 lib/mqtt.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/mqtt.c b/lib/mqtt.c
index e79bd3b482..9bcbaa1950 100644
--- a/lib/mqtt.c
+++ b/lib/mqtt.c
@@ -732,8 +732,14 @@ static CURLcode mqtt_doing(struct Curl_easy *data, bool *done)
   case MQTT_FIRST:
     /* Read the initial byte only */
     result = Curl_read(data, sockfd, (char *)&mq->firstbyte, 1, &nread);
-    if(!nread)
+    if(result)
+      break;
+    else if(!nread) {
+      failf(data, "Connection disconnected");
+      *done = TRUE;
+      result = CURLE_RECV_ERROR;
       break;
+    }
     Curl_debug(data, CURLINFO_HEADER_IN, (char *)&mq->firstbyte, 1);
     /* remember the first byte */
     mq->npacket = 0;
-- 
2.47.3