Avoid failures due to bad payload selection

Author: jvazquez-r7

modules/exploits/multi/http/apache_mod_cgi_bash_env_exec.rb

@@ -68,6 +68,12 @@ def check
   end
 
   def exploit
+    # Cannot use generic/shell_reverse_tcp inside an elf
+    # Checking before proceeds
+    if generate_payload_exe.blank?
+      fail_with(Failure::BadConfig, "#{peer} - Failed to store payload inside executable, please select a native payload")
+    end
+
     execute_cmdstager(:linemax => datastore['CMD_MAX_LENGTH'])
   end