From a39e2d17ad9824dc69f678fb0e652467655ad7a0 Mon Sep 17 00:00:00 2001
From: Tautvilis <tautvilis@gmail.com>
Date: Tue, 1 Sep 2026 07:37:54 +0000
Subject: [PATCH] modbus-tcp: check if response slave id matches request slave
 id

---
 src/modbus-tcp.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/modbus-tcp.c b/src/modbus-tcp.c
index e84dc6028..37695b02e 100644
--- a/src/modbus-tcp.c
+++ b/src/modbus-tcp.c
@@ -225,6 +225,18 @@ static int _modbus_tcp_pre_check_confirmation(modbus_t *ctx,
         return -1;
     }
 
+    /* Check if response slave ID matches request slave ID*/
+    if (req[6] != rsp[6]) {
+        if (ctx->debug) {
+            fprintf(stderr,
+                    "The responding slave %d isn't the requested slave %d\n",
+                    rsp[6],
+                    req[6]);
+        }
+        errno = EMBBADSLAVE;
+        return -1;
+    }
+
     return 0;
 }