diff --git a/MdeModulePkg/Universal/HiiDatabaseDxe/String.c b/MdeModulePkg/Universal/HiiDatabaseDxe/String.c
index 505e063d49..2c7ecfea40 100644
--- a/MdeModulePkg/Universal/HiiDatabaseDxe/String.c
+++ b/MdeModulePkg/Universal/HiiDatabaseDxe/String.c
@@ -2,7 +2,7 @@
 Implementation for EFI_HII_STRING_PROTOCOL.
 
 
-Copyright (c) 2007 - 2018, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2007 - 2020, Intel Corporation. All rights reserved.<BR>
 (C) Copyright 2016 Hewlett Packard Enterprise Development LP<BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -1006,6 +1006,7 @@ SetStringWorker (
       TmpSize
       );
 
+    ZeroMem (StringPackage->StringBlock, OldBlockSize);
     FreePool (StringPackage->StringBlock);
     StringPackage->StringBlock = Block;
     StringPackage->StringPkgHdr->Header.Length += (UINT32) (BlockSize - OldBlockSize);
@@ -1039,6 +1040,7 @@ SetStringWorker (
       OldBlockSize - (StringTextPtr - StringPackage->StringBlock) - StringSize
       );
 
+    ZeroMem (StringPackage->StringBlock, OldBlockSize);
     FreePool (StringPackage->StringBlock);
     StringPackage->StringBlock = Block;
     StringPackage->StringPkgHdr->Header.Length += (UINT32) (BlockSize - OldBlockSize);
@@ -1090,6 +1092,7 @@ SetStringWorker (
 
   CopyMem (BlockPtr, StringPackage->StringBlock, OldBlockSize);
 
+  ZeroMem (StringPackage->StringBlock, OldBlockSize);
   FreePool (StringPackage->StringBlock);
   StringPackage->StringBlock = Block;
   StringPackage->StringPkgHdr->Header.Length += Ext2.Length;
@@ -1275,6 +1278,7 @@ HiiNewString (
       // Append a EFI_HII_SIBT_END block to the end.
       //
       *BlockPtr = EFI_HII_SIBT_END;
+      ZeroMem (StringPackage->StringBlock, OldBlockSize);
       FreePool (StringPackage->StringBlock);
       StringPackage->StringBlock = StringBlock;
       StringPackage->StringPkgHdr->Header.Length += Ucs2BlockSize;
@@ -1406,6 +1410,7 @@ HiiNewString (
     // Append a EFI_HII_SIBT_END block to the end.
     //
     *BlockPtr = EFI_HII_SIBT_END;
+    ZeroMem (StringPackage->StringBlock, OldBlockSize);
     FreePool (StringPackage->StringBlock);
     StringPackage->StringBlock = StringBlock;
     StringPackage->StringPkgHdr->Header.Length += Ucs2BlockSize;
@@ -1448,6 +1453,7 @@ HiiNewString (
       // Append a EFI_HII_SIBT_END block to the end.
       //
       *BlockPtr = EFI_HII_SIBT_END;
+      ZeroMem (StringPackage->StringBlock, OldBlockSize);
       FreePool (StringPackage->StringBlock);
       StringPackage->StringBlock = StringBlock;
       StringPackage->StringPkgHdr->Header.Length += Ucs2FontBlockSize;
@@ -1509,6 +1515,7 @@ HiiNewString (
       // Append a EFI_HII_SIBT_END block to the end.
       //
       *BlockPtr = EFI_HII_SIBT_END;
+      ZeroMem (StringPackage->StringBlock, OldBlockSize);
       FreePool (StringPackage->StringBlock);
       StringPackage->StringBlock = StringBlock;
       StringPackage->StringPkgHdr->Header.Length += FontBlockSize + Ucs2FontBlockSize;