diff --git a/MdeModulePkg/Core/Dxe/DxeMain.inf b/MdeModulePkg/Core/Dxe/DxeMain.inf
index 903e64099b..5862740b9a 100644
--- a/MdeModulePkg/Core/Dxe/DxeMain.inf
+++ b/MdeModulePkg/Core/Dxe/DxeMain.inf
@@ -99,6 +99,7 @@
   ImagePropertiesRecordLib
   DxeMemoryProtectionHobLib        ## MU_CHANGE
   MemoryBinOverrideLib      ## MU_CHANGE
+  SafeIntLib                ## MU_CHANGE
 
 [Guids]
   gEfiEventMemoryMapChangeGuid                  ## PRODUCES             ## Event
diff --git a/MdeModulePkg/Core/Dxe/Misc/MemoryProtectionSupport.c b/MdeModulePkg/Core/Dxe/Misc/MemoryProtectionSupport.c
index 0f6b878e7d..81776fadca 100644
--- a/MdeModulePkg/Core/Dxe/Misc/MemoryProtectionSupport.c
+++ b/MdeModulePkg/Core/Dxe/Misc/MemoryProtectionSupport.c
@@ -5,6 +5,7 @@
   SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
 
+#include <Library/SafeIntLib.h>
 #include "MemoryProtectionSupport.h"
 
 IMAGE_PROPERTIES_PRIVATE_DATA  mImagePropertiesPrivate = {
@@ -66,6 +67,8 @@ BOOLEAN                        mGcdSyncComplete                = FALSE;
 // TRUE if A is a bitwise subset of B
 #define CHECK_SUBSET(A, B)  ((A | B) == B)
 
+#define LEGACY_BIOS_WB_LENGTH  0xA0000
+
 /**
   Return the section alignment requirement for the PE image section type.
 
@@ -2855,6 +2858,17 @@ DisableNullDetection (
     return;
   }
 
+  // Only re-enable the null page if it is system memory. If this page belongs to
+  // another memory type or is unmapped in general, leave it RP
+  if (Desc.GcdMemoryType != EfiGcdMemoryTypeSystemMemory) {
+    DEBUG ((
+      DEBUG_WARN,
+      "%a - Not disabling null detection as page 0 is not marked as system memory\n",
+      __func__
+      ));
+    return;
+  }
+
   Status = CoreSetMemorySpaceAttributes (
              0,
              EFI_PAGE_SIZE,
@@ -2941,21 +2955,122 @@ MapLegacyBiosMemoryRWX (
   VOID
   )
 {
-  EFI_STATUS  Status = EFI_SUCCESS;
+  EFI_STATUS                       Status = EFI_SUCCESS;
+  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  Desc;
+  EFI_PHYSICAL_ADDRESS             Start = 0x0;
+  UINT64                           Length;
+  UINT64                           DescLengthFromStart;
 
-  // https://wiki.osdev.org/Memory_Map_(x86)
-  //
-  // Map the legacy BIOS write-back memory as RWX.
-  if (gCpu != NULL) {
+  if (gCpu == NULL) {
+    DEBUG ((
+      DEBUG_ERROR,
+      "%a cannot remap Legacy BIOS memory as RWX because gCpu is NULL\n",
+      __func__
+      ));
+    return;
+  }
+
+  // Ensure that this memory is marked as system memory. If it is not system memory, do not change
+  // the memory attributes as we do not want to map something that shouldn't be mapped or map something
+  // incorrectly
+  while (Start < LEGACY_BIOS_WB_LENGTH) {
+    Status = CoreGetMemorySpaceDescriptor (Start, &Desc);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a - Failed to get memory space descriptor for address 0x%llx! Status = %r\n",
+        __func__,
+        Start,
+        Status
+        ));
+      return;
+    }
+
+    // find the length from Start to the end of this descriptor, in the case Start != Desc.BaseAddress
+    // these should all be well formed descriptors, but use SafeIntLib functions just to be sure we don't
+    // over/underflow
+    Status = SafeUint64Add (Desc.BaseAddress, Desc.Length, &DescLengthFromStart);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a - Memory space descriptor has UINT64 overflowing address 0x%llx + length 0x%llx! Status = %r\n",
+        __func__,
+        Desc.BaseAddress,
+        Desc.Length,
+        Status
+        ));
+
+      // if we fail here this is very bad and means the GCD is malformed
+      ASSERT (FALSE);
+      return;
+    }
+
+    Status = SafeUint64Sub (DescLengthFromStart, Start, &DescLengthFromStart);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a - Memory space descriptor has UINT64 underflowing address 0x%llx + length 0x%llx Start: 0x%llx! Status = %r\n",
+        __func__,
+        Desc.BaseAddress,
+        Desc.Length,
+        Start,
+        Status
+        ));
+
+      // if we fail here this is very bad and means the GCD is malformed
+      ASSERT (FALSE);
+      return;
+    }
+
+    // Ensure we only go up to LEGACY_BIOS_WB_LENGTH here, we know Start is less than it due to while condition
+    // We also know Start + DescLengthFromStart won't overflow because above we did a safe subtraction of Start from
+    // DescLengthFromStart
+    if (Start + DescLengthFromStart > LEGACY_BIOS_WB_LENGTH) {
+      Length = LEGACY_BIOS_WB_LENGTH - Start;
+    } else {
+      Length = DescLengthFromStart;
+    }
+
+    // remove this chunk from being remapped if it is not system memory
+    if (Desc.GcdMemoryType != EfiGcdMemoryTypeSystemMemory) {
+      DEBUG ((
+        DEBUG_WARN,
+        "%a Not mapping 0x%llx for 0x%llx as RWX because it is not system memory\n",
+        __func__,
+        Desc.BaseAddress,
+        Length
+        ));
+
+      // we know this doesn't overflow because we did a safe subtraction of Start from DescLengthFromStart above
+      Start += DescLengthFromStart;
+      continue;
+    }
+
+    // https://wiki.osdev.org/Memory_Map_(x86)
+    //
+    // Map the legacy BIOS write-back memory as RWX.
     Status = gCpu->SetMemoryAttributes (
                      gCpu,
-                     0x0,
-                     0xa0000,
+                     Start,
+                     Length,
                      0
                      );
-  }
 
-  ASSERT_EFI_ERROR (Status);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a failed to map 0x%llx for length 0x%llx as RWX\n",
+        __func__,
+        Start,
+        Length
+        ));
+
+      ASSERT_EFI_ERROR (Status);
+    }
+
+    // we know this doesn't overflow because we did a safe subtraction of Start from DescLengthFromStart above
+    Start += DescLengthFromStart;
+  }
 }
 
 /**