diff --git a/src/libraries/Common/src/Interop/BSD/System.Native/Interop.TcpConnectionInfo.cs b/src/libraries/Common/src/Interop/BSD/System.Native/Interop.TcpConnectionInfo.cs
index 58f6501a825c9e..946059dc870934 100644
--- a/src/libraries/Common/src/Interop/BSD/System.Native/Interop.TcpConnectionInfo.cs
+++ b/src/libraries/Common/src/Interop/BSD/System.Native/Interop.TcpConnectionInfo.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Net.NetworkInformation;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop
@@ -9,9 +10,9 @@ internal static partial class Interop
     internal static partial class Sys
     {
         [StructLayout(LayoutKind.Sequential)]
-        public unsafe struct IPEndPointInfo
+        public struct IPEndPointInfo
         {
-            public fixed byte AddressBytes[16];
+            public InlineArray16<byte> AddressBytes;
             public uint NumAddressBytes;
             public uint Port;
             private uint __padding; // For native struct-size padding. Does not contain useful data.
diff --git a/src/libraries/Common/src/Interop/Unix/System.Native/Interop.EnumerateInterfaceAddresses.cs b/src/libraries/Common/src/Interop/Unix/System.Native/Interop.EnumerateInterfaceAddresses.cs
index cb237ff1f1b2cc..99bfb7cba730b5 100644
--- a/src/libraries/Common/src/Interop/Unix/System.Native/Interop.EnumerateInterfaceAddresses.cs
+++ b/src/libraries/Common/src/Interop/Unix/System.Native/Interop.EnumerateInterfaceAddresses.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop
@@ -8,38 +9,38 @@ internal static partial class Interop
     internal static partial class Sys
     {
         [StructLayout(LayoutKind.Sequential)]
-        public unsafe struct LinkLayerAddressInfo
+        public struct LinkLayerAddressInfo
         {
             public int InterfaceIndex;
-            public fixed byte AddressBytes[8];
+            public InlineArray8<byte> AddressBytes;
             public byte NumAddressBytes;
             private byte __padding; // For native struct-size padding. Does not contain useful data.
             public ushort HardwareType;
         }
 
         [StructLayout(LayoutKind.Sequential)]
-        public unsafe struct IpAddressInfo
+        public struct IpAddressInfo
         {
             public int InterfaceIndex;
-            public fixed byte AddressBytes[16];
+            public InlineArray16<byte> AddressBytes;
             public byte NumAddressBytes;
             public byte PrefixLength;
-            private fixed byte __padding[2];
+            private InlineArray2<byte> __padding;
         }
 
         [StructLayout(LayoutKind.Sequential)]
-        public unsafe struct NetworkInterfaceInfo
+        public struct NetworkInterfaceInfo
         {
-            public fixed byte Name[16];
+            public InlineArray16<byte> Name;
             public long Speed;
             public int InterfaceIndex;
             public int Mtu;
             public ushort HardwareType;
             public byte OperationalState;
             public byte NumAddressBytes;
-            public fixed byte AddressBytes[8];
+            public InlineArray8<byte> AddressBytes;
             public byte SupportsMulticast;
-            private fixed byte __padding[3];
+            private InlineArray3<byte> __padding;
         }
 
         [LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_EnumerateInterfaceAddresses")]
diff --git a/src/libraries/Common/src/Interop/Windows/Kernel32/Interop.TimeZone.cs b/src/libraries/Common/src/Interop/Windows/Kernel32/Interop.TimeZone.cs
index 705d97ac3f48d2..f9cd8549db16c1 100644
--- a/src/libraries/Common/src/Interop/Windows/Kernel32/Interop.TimeZone.cs
+++ b/src/libraries/Common/src/Interop/Windows/Kernel32/Interop.TimeZone.cs
@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop
@@ -30,37 +32,56 @@ internal bool Equals(in SYSTEMTIME other) =>
         }
 
         [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
-        internal unsafe struct TIME_DYNAMIC_ZONE_INFORMATION
+        internal struct TIME_DYNAMIC_ZONE_INFORMATION
         {
+            [InlineArray(32)]
+            internal struct NameBuffer
+            {
+                private char _element0;
+            }
+
+            [InlineArray(128)]
+            internal struct TimeZoneKeyNameBuffer
+            {
+                private char _element0;
+            }
+
             internal int Bias;
-            internal fixed char StandardName[32];
+            internal NameBuffer StandardName;
             internal SYSTEMTIME StandardDate;
             internal int StandardBias;
-            internal fixed char DaylightName[32];
+            internal NameBuffer DaylightName;
             internal SYSTEMTIME DaylightDate;
             internal int DaylightBias;
-            internal fixed char TimeZoneKeyName[128];
+            internal TimeZoneKeyNameBuffer TimeZoneKeyName;
             internal byte DynamicDaylightTimeDisabled;
 
             internal string GetTimeZoneKeyName()
             {
-                fixed (char* p = TimeZoneKeyName)
-                    return new string(p);
+                ReadOnlySpan<char> span = TimeZoneKeyName;
+                int idx = span.IndexOf('\0');
+                return new string(idx >= 0 ? span[..idx] : span);
             }
         }
 
         [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
-        internal unsafe struct TIME_ZONE_INFORMATION
+        internal struct TIME_ZONE_INFORMATION
         {
+            [InlineArray(32)]
+            internal struct NameBuffer
+            {
+                private char _element0;
+            }
+
             internal int Bias;
-            internal fixed char StandardName[32];
+            internal NameBuffer StandardName;
             internal SYSTEMTIME StandardDate;
             internal int StandardBias;
-            internal fixed char DaylightName[32];
+            internal NameBuffer DaylightName;
             internal SYSTEMTIME DaylightDate;
             internal int DaylightBias;
 
-            internal TIME_ZONE_INFORMATION(in TIME_DYNAMIC_ZONE_INFORMATION dtzi)
+            internal unsafe TIME_ZONE_INFORMATION(in TIME_DYNAMIC_ZONE_INFORMATION dtzi)
             {
                 // The start of TIME_DYNAMIC_ZONE_INFORMATION has identical layout as TIME_ZONE_INFORMATION
                 fixed (TIME_ZONE_INFORMATION* pTo = &this)
@@ -70,14 +91,16 @@ internal TIME_ZONE_INFORMATION(in TIME_DYNAMIC_ZONE_INFORMATION dtzi)
 
             internal string GetStandardName()
             {
-                fixed (char* p = StandardName)
-                    return new string(p);
+                ReadOnlySpan<char> span = StandardName;
+                int idx = span.IndexOf('\0');
+                return new string(idx >= 0 ? span[..idx] : span);
             }
 
             internal string GetDaylightName()
             {
-                fixed (char* p = DaylightName)
-                    return new string(p);
+                ReadOnlySpan<char> span = DaylightName;
+                int idx = span.IndexOf('\0');
+                return new string(idx >= 0 ? span[..idx] : span);
             }
         }
 
diff --git a/src/libraries/Common/src/Interop/Windows/NtDll/Interop.RtlGetVersion.cs b/src/libraries/Common/src/Interop/Windows/NtDll/Interop.RtlGetVersion.cs
index 3fb9740a7f2490..7e9a8f5cb7a679 100644
--- a/src/libraries/Common/src/Interop/Windows/NtDll/Interop.RtlGetVersion.cs
+++ b/src/libraries/Common/src/Interop/Windows/NtDll/Interop.RtlGetVersion.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 internal static partial class Interop
@@ -8,24 +9,35 @@ internal static partial class Interop
     internal static partial class NtDll
     {
         [LibraryImport(Libraries.NtDll)]
-        private static partial int RtlGetVersion(ref RTL_OSVERSIONINFOEX lpVersionInformation);
+        private static unsafe partial int RtlGetVersion(RTL_OSVERSIONINFOEX* lpVersionInformation);
 
         internal static unsafe int RtlGetVersionEx(out RTL_OSVERSIONINFOEX osvi)
         {
             osvi = default;
             osvi.dwOSVersionInfoSize = (uint)sizeof(RTL_OSVERSIONINFOEX);
-            return RtlGetVersion(ref osvi);
+            fixed (RTL_OSVERSIONINFOEX* p = &osvi)
+                return RtlGetVersion(p);
         }
 
         [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
-        internal unsafe struct RTL_OSVERSIONINFOEX
+        internal struct RTL_OSVERSIONINFOEX
         {
             internal uint dwOSVersionInfoSize;
             internal uint dwMajorVersion;
             internal uint dwMinorVersion;
             internal uint dwBuildNumber;
             internal uint dwPlatformId;
-            internal fixed char szCSDVersion[128];
+#if NET
+            internal CSDVersionBuffer szCSDVersion;
+
+            [InlineArray(128)]
+            internal struct CSDVersionBuffer
+            {
+                private char _element0;
+            }
+#else
+            internal unsafe fixed char szCSDVersion[128];
+#endif
         }
     }
 }
diff --git a/src/libraries/Common/src/Interop/Windows/WinHttp/Interop.winhttp_types.cs b/src/libraries/Common/src/Interop/Windows/WinHttp/Interop.winhttp_types.cs
index 42b58b7df198d7..cc8fbfeb926d9d 100644
--- a/src/libraries/Common/src/Interop/Windows/WinHttp/Interop.winhttp_types.cs
+++ b/src/libraries/Common/src/Interop/Windows/WinHttp/Interop.winhttp_types.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 #if NET
 using System.Runtime.InteropServices.Marshalling;
@@ -337,14 +338,25 @@ public struct WINHTTP_ASYNC_RESULT
         }
 
         [StructLayout(LayoutKind.Sequential)]
-        public unsafe struct WINHTTP_CONNECTION_INFO
+        public struct WINHTTP_CONNECTION_INFO
         {
             // This field is actually 4 bytes, but we use nuint to avoid alignment issues for x64.
             // If we want to read this field in the future, we need to change type and make sure
             // alignment is correct for necessary archs.
             public nuint cbSize;
-            public fixed byte LocalAddress[128];
-            public fixed byte RemoteAddress[128];
+#if NET
+            public AddressBuffer LocalAddress;
+            public AddressBuffer RemoteAddress;
+
+            [InlineArray(128)]
+            public struct AddressBuffer
+            {
+                private byte _element0;
+            }
+#else
+            public unsafe fixed byte LocalAddress[128];
+            public unsafe fixed byte RemoteAddress[128];
+#endif
         }
 
         [StructLayout(LayoutKind.Sequential)]
diff --git a/src/libraries/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpRequestCallback.cs b/src/libraries/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpRequestCallback.cs
index 4ce5a952b45253..f90327e07cd994 100644
--- a/src/libraries/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpRequestCallback.cs
+++ b/src/libraries/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpRequestCallback.cs
@@ -330,7 +330,11 @@ private static void OnRequestSendingRequest(WinHttpRequestState state)
                             // See: https://learn.microsoft.com/en-us/windows/win32/api/winhttp/ns-winhttp-winhttp_connection_info
                             // SOCKADDR_STORAGE can hold either IPv4 or IPv6 address.
                             // For offset numbers: https://learn.microsoft.com/en-us/windows/win32/winsock/sockaddr-2
+#if NET
+                            ReadOnlySpan<byte> remoteAddressSpan = connectionInfo.RemoteAddress;
+#else
                             ReadOnlySpan<byte> remoteAddressSpan = new ReadOnlySpan<byte>(connectionInfo.RemoteAddress, 128);
+#endif
                             AddressFamily addressFamily = (AddressFamily)(remoteAddressSpan[0] + (remoteAddressSpan[1] << 8));
                             ipAddress = addressFamily switch
                             {
diff --git a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/AndroidNetworkInterface.cs b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/AndroidNetworkInterface.cs
index dcf66895aea7b1..7a331560c69932 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/AndroidNetworkInterface.cs
+++ b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/AndroidNetworkInterface.cs
@@ -19,7 +19,7 @@ internal unsafe AndroidNetworkInterface(string name, Interop.Sys.NetworkInterfac
             _index = networkInterfaceInfo->InterfaceIndex;
             if (networkInterfaceInfo->NumAddressBytes > 0)
             {
-                _physicalAddress = new PhysicalAddress(new ReadOnlySpan<byte>(networkInterfaceInfo->AddressBytes, networkInterfaceInfo->NumAddressBytes).ToArray());
+                _physicalAddress = new PhysicalAddress(((ReadOnlySpan<byte>)networkInterfaceInfo->AddressBytes)[..networkInterfaceInfo->NumAddressBytes].ToArray());
             }
 
             _mtu = networkInterfaceInfo->Mtu;
@@ -33,7 +33,7 @@ internal unsafe AndroidNetworkInterface(string name, Interop.Sys.NetworkInterfac
 
         internal unsafe void AddAddress(Interop.Sys.IpAddressInfo *addressInfo)
         {
-            var address = new IPAddress(new ReadOnlySpan<byte>(addressInfo->AddressBytes, addressInfo->NumAddressBytes));
+            var address = new IPAddress(((ReadOnlySpan<byte>)addressInfo->AddressBytes)[..addressInfo->NumAddressBytes]);
             if (address.IsIPv6LinkLocal)
             {
                 address.ScopeId = addressInfo->InterfaceIndex;
diff --git a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIPGlobalProperties.cs b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIPGlobalProperties.cs
index 448d2181e9b074..c01b320866b282 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIPGlobalProperties.cs
+++ b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIPGlobalProperties.cs
@@ -32,12 +32,12 @@ private unsafe TcpConnectionInformation[] GetTcpConnections(bool listeners)
                     continue;
                 }
 
-                IPAddress localIPAddress = new IPAddress(new ReadOnlySpan<byte>(nativeInfo.LocalEndPoint.AddressBytes, checked((int)nativeInfo.LocalEndPoint.NumAddressBytes)));
+                IPAddress localIPAddress = new IPAddress(((ReadOnlySpan<byte>)nativeInfo.LocalEndPoint.AddressBytes)[..checked((int)nativeInfo.LocalEndPoint.NumAddressBytes)]);
                 IPEndPoint local = new IPEndPoint(localIPAddress, (int)nativeInfo.LocalEndPoint.Port);
 
                 IPAddress remoteIPAddress = nativeInfo.RemoteEndPoint.NumAddressBytes == 0 ?
                     IPAddress.Any :
-                    new IPAddress(new ReadOnlySpan<byte>(nativeInfo.RemoteEndPoint.AddressBytes, checked((int)nativeInfo.RemoteEndPoint.NumAddressBytes)));
+                    new IPAddress(((ReadOnlySpan<byte>)nativeInfo.RemoteEndPoint.AddressBytes)[..checked((int)nativeInfo.RemoteEndPoint.NumAddressBytes)]);
 
                 IPEndPoint remote = new IPEndPoint(remoteIPAddress, (int)nativeInfo.RemoteEndPoint.Port);
                 connectionInformations[nextResultIndex++] = new SimpleTcpConnectionInformation(local, remote, state);
@@ -87,7 +87,7 @@ public override unsafe IPEndPoint[] GetActiveUdpListeners()
                 int port = (int)endPointInfo.Port;
                 IPAddress ipAddress = endPointInfo.NumAddressBytes == 0 ?
                     IPAddress.Any :
-                    new IPAddress(new ReadOnlySpan<byte>(endPointInfo.AddressBytes, checked((int)endPointInfo.NumAddressBytes)));
+                    new IPAddress(((ReadOnlySpan<byte>)endPointInfo.AddressBytes)[..checked((int)endPointInfo.NumAddressBytes)]);
 
                 endPoints[i] = new IPEndPoint(ipAddress, port);
             }
diff --git a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIpInterfaceProperties.cs b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIpInterfaceProperties.cs
index 8ce6f541bf0de9..0b25c83c83465e 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIpInterfaceProperties.cs
+++ b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/BsdIpInterfaceProperties.cs
@@ -93,7 +93,7 @@ private static unsafe void OnGatewayFound(void* pContext, Interop.Sys.IpAddressI
         {
             Context* context = (Context*)pContext;
 
-            IPAddress ipAddress = new IPAddress(new ReadOnlySpan<byte>(gatewayAddressInfo->AddressBytes, gatewayAddressInfo->NumAddressBytes));
+            IPAddress ipAddress = new IPAddress(((ReadOnlySpan<byte>)gatewayAddressInfo->AddressBytes)[..gatewayAddressInfo->NumAddressBytes]);
             if (ipAddress.IsIPv6LinkLocal)
             {
                 // For Link-Local addresses add ScopeId as that is not part of the route entry.
diff --git a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/IPAddressUtil.cs b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/IPAddressUtil.cs
index c2e776a07bee0c..9a2ef06a50d40e 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/IPAddressUtil.cs
+++ b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/IPAddressUtil.cs
@@ -34,7 +34,7 @@ public static bool IsMulticast(IPAddress address)
         /// <returns>A new IPAddress created with the information in the native structure.</returns>
         public static unsafe IPAddress GetIPAddressFromNativeInfo(Interop.Sys.IpAddressInfo* addressInfo)
         {
-            IPAddress ipAddress = new IPAddress(new ReadOnlySpan<byte>(addressInfo->AddressBytes, addressInfo->NumAddressBytes));
+            IPAddress ipAddress = new IPAddress(((ReadOnlySpan<byte>)addressInfo->AddressBytes)[..addressInfo->NumAddressBytes]);
             return ipAddress;
         }
     }
diff --git a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/LinuxNetworkInterface.cs b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/LinuxNetworkInterface.cs
index 71330d0eb9ddc7..0310e630b7cda9 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/LinuxNetworkInterface.cs
+++ b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/LinuxNetworkInterface.cs
@@ -95,7 +95,7 @@ public static unsafe NetworkInterface[] GetLinuxNetworkInterfaces()
 
                 for (int i = 0; i < interfaceCount; i++)
                 {
-                    var lni = new LinuxNetworkInterface(Utf8StringMarshaller.ConvertToManaged(nii->Name)!, nii->InterfaceIndex, systemProperties);
+                    var lni = new LinuxNetworkInterface(Utf8StringMarshaller.ConvertToManaged((byte*)&nii->Name)!, nii->InterfaceIndex, systemProperties);
                     lni._interfaceType = (NetworkInterfaceType)nii->HardwareType;
                     lni._speed = nii->Speed;
                     lni._operationalStatus = (OperationalStatus)nii->OperationalState;
@@ -104,7 +104,7 @@ public static unsafe NetworkInterface[] GetLinuxNetworkInterfaces()
 
                     if (nii->NumAddressBytes > 0)
                     {
-                        lni._physicalAddress = new PhysicalAddress(new ReadOnlySpan<byte>(nii->AddressBytes, nii->NumAddressBytes).ToArray());
+                        lni._physicalAddress = new PhysicalAddress(((ReadOnlySpan<byte>)nii->AddressBytes)[..nii->NumAddressBytes].ToArray());
                     }
 
                     interfaces[i] = lni;
@@ -114,7 +114,7 @@ public static unsafe NetworkInterface[] GetLinuxNetworkInterfaces()
 
                 while (addressCount != 0)
                 {
-                    var address = new IPAddress(new ReadOnlySpan<byte>(ai->AddressBytes, ai->NumAddressBytes));
+                    var address = new IPAddress(((ReadOnlySpan<byte>)ai->AddressBytes)[..ai->NumAddressBytes]);
                     if (address.IsIPv6LinkLocal)
                     {
                         address.ScopeId = ai->InterfaceIndex;
diff --git a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/NetworkInterfacePal.Android.cs b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/NetworkInterfacePal.Android.cs
index 565d8df9ab4b6e..8bc48a35dd3318 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/NetworkInterfacePal.Android.cs
+++ b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/NetworkInterfacePal.Android.cs
@@ -52,7 +52,7 @@ private static unsafe AndroidNetworkInterface[] ToAndroidNetworkInterfaceArray(i
             var networkInterfaceInfo = (Interop.Sys.NetworkInterfaceInfo*)networkInterfacesPtr;
             for (int i = 0; i < interfaceCount; i++, networkInterfaceInfo++)
             {
-                var name = Utf8StringMarshaller.ConvertToManaged(networkInterfaceInfo->Name);
+                var name = Utf8StringMarshaller.ConvertToManaged((byte*)&networkInterfaceInfo->Name);
                 networkInterfaces[i] = new AndroidNetworkInterface(name!, networkInterfaceInfo);
             }
 
diff --git a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/UnixNetworkInterface.cs b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/UnixNetworkInterface.cs
index 444d19bf01a42b..78b655131860f7 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/UnixNetworkInterface.cs
+++ b/src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/UnixNetworkInterface.cs
@@ -98,11 +98,7 @@ protected unsafe void ProcessIpv6Address(Interop.Sys.IpAddressInfo* addressInfo,
 
         protected unsafe void ProcessLinkLayerAddress(Interop.Sys.LinkLayerAddressInfo* llAddr)
         {
-            byte[] macAddress = new byte[llAddr->NumAddressBytes];
-            fixed (byte* macAddressPtr = macAddress)
-            {
-                Buffer.MemoryCopy(llAddr->AddressBytes, macAddressPtr, llAddr->NumAddressBytes, llAddr->NumAddressBytes);
-            }
+            byte[] macAddress = ((ReadOnlySpan<byte>)llAddr->AddressBytes)[..llAddr->NumAddressBytes].ToArray();
             PhysicalAddress physicalAddress = new PhysicalAddress(macAddress);
 
             _index = llAddr->InterfaceIndex;
diff --git a/src/libraries/System.Private.CoreLib/src/System/Environment.Windows.cs b/src/libraries/System.Private.CoreLib/src/System/Environment.Windows.cs
index 80624afcb23a44..83ab7e5b8ee0da 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Environment.Windows.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Environment.Windows.cs
@@ -141,7 +141,7 @@ private static unsafe bool IsPrivilegedProcessCore()
             return builder.ToString();
         }
 
-        private static unsafe OperatingSystem GetOSVersion()
+        private static OperatingSystem GetOSVersion()
         {
             if (Interop.NtDll.RtlGetVersionEx(out Interop.NtDll.RTL_OSVERSIONINFOEX osvi) != 0)
             {
@@ -150,9 +150,14 @@ private static unsafe OperatingSystem GetOSVersion()
 
             var version = new Version((int)osvi.dwMajorVersion, (int)osvi.dwMinorVersion, (int)osvi.dwBuildNumber, 0);
 
-            return osvi.szCSDVersion[0] != '\0' ?
-                new OperatingSystem(PlatformID.Win32NT, version, new string(&osvi.szCSDVersion[0])) :
-                new OperatingSystem(PlatformID.Win32NT, version);
+            if (osvi.szCSDVersion[0] != '\0')
+            {
+                ReadOnlySpan<char> csd = osvi.szCSDVersion;
+                int idx = csd.IndexOf('\0');
+                return new OperatingSystem(PlatformID.Win32NT, version, new string(idx >= 0 ? csd[..idx] : csd));
+            }
+
+            return new OperatingSystem(PlatformID.Win32NT, version);
         }
 
         private static string? s_systemDirectory;
diff --git a/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.Ascii.cs b/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.Ascii.cs
index d66560a5286dda..d11ad896b86966 100644
--- a/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.Ascii.cs
+++ b/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.Ascii.cs
@@ -21,7 +21,17 @@ internal sealed partial class OptimizedInboxTextEncoder
         /// </summary>
         private unsafe struct AsciiPreescapedData
         {
-            private fixed ulong Data[128];
+#if NET
+            [InlineArray(128)]
+            private struct DataBuffer
+            {
+                private ulong _element0;
+            }
+
+            private DataBuffer Data;
+#else
+            private unsafe fixed ulong Data[128];
+#endif
 
             internal void PopulatePreescapedData(in AllowedBmpCodePointsBitmap allowedCodePointsBmp, ScalarEscaperBase innerEncoder)
             {
@@ -63,7 +73,7 @@ internal readonly bool TryGetPreescapedData(uint codePoint, out ulong preescaped
             {
                 if (codePoint <= 0x7F)
                 {
-                    preescapedData = Data[codePoint];
+                    preescapedData = Data[(int)codePoint];
                     return true;
                 }
                 else
diff --git a/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilConverter.cs b/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilConverter.cs
index 820d38631706e0..8afebfe53b7952 100644
--- a/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilConverter.cs
+++ b/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilConverter.cs
@@ -115,7 +115,7 @@ public unsafe void GatherInfo(PEReader peReader, out WCFileInfo wcInfo, out PEFi
         var peHeader = headers.PEHeader!;
         var coffHeader = headers.CoffHeader!;
         var sections = headers.SectionHeaders;
-        WebcilHeader header;
+        WebcilHeader header = default;
         header.Id[0] = (byte)'W';
         header.Id[1] = (byte)'b';
         header.Id[2] = (byte)'I';
diff --git a/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilHeader.cs b/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilHeader.cs
index 419e058bd180f2..9705e584951bdc 100644
--- a/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilHeader.cs
+++ b/src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilHeader.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 namespace Microsoft.NET.WebAssembly.Webcil;
@@ -13,9 +14,13 @@ namespace Microsoft.NET.WebAssembly.Webcil;
 /// The header is a subset of the PE, COFF and CLI headers that are needed by the mono runtime to load managed assemblies.
 /// </remarks>
 [StructLayout(LayoutKind.Sequential, Pack = 1)]
-public unsafe struct WebcilHeader
+public struct WebcilHeader
 {
-    public fixed byte Id[4];
+#if NET
+    public InlineArray4<byte> Id;
+#else
+    public unsafe fixed byte Id[4];
+#endif
     // 4 bytes
     public ushort VersionMajor;
     public ushort VersionMinor;