diff --git a/sql/auth/sql_authentication.cc b/sql/auth/sql_authentication.cc
--- a/sql/auth/sql_authentication.cc
+++ b/sql/auth/sql_authentication.cc
@@ -2152,6 +2152,7 @@ static bool parse_com_change_user_packet(THD *thd, MPVIO_EXT *mpvio,
   if (ptr + 1 < end) {
     if (mpvio->charset_adapter->init_client_charset(uint2korr(ptr)))
       return true;
+    ptr = ptr + 2;
   }
 
   /* Convert database and user names to utf8 */
@@ -2189,17 +2190,17 @@ static bool parse_com_change_user_packet(THD *thd, MPVIO_EXT *mpvio,
 
   const char *client_plugin;
   if (protocol->has_client_capability(CLIENT_PLUGIN_AUTH)) {
-    client_plugin = ptr + 2;
-    /*
-      ptr needs to be updated to point to correct position so that
-      connection attributes are read properly.
-    */
-    ptr = ptr + 2 + strlen(client_plugin) + 1;
-
+    client_plugin = ptr;
     if (client_plugin >= end) {
       my_error(ER_UNKNOWN_COM_ERROR, MYF(0));
       return true;
     }
+
+    /*
+      ptr needs to be updated to point to correct position so that
+      connection attributes are read properly.
+    */
+    ptr = ptr + strlen(client_plugin) + 1;
   } else
     client_plugin = Cached_authentication_plugins::get_plugin_name(
         PLUGIN_MYSQL_NATIVE_PASSWORD);