diff --git a/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHelpers.cs b/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHelpers.cs
index 898daf1e6c3ed7..946f668dc4a346 100644
--- a/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHelpers.cs
+++ b/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHelpers.cs
@@ -202,19 +202,18 @@ internal static TarEntryType GetCorrectTypeFlagForFormat(TarEntryFormat format,
         /// <summary>Parses a byte span that represents an ASCII string containing a number in octal base.</summary>
         internal static T ParseOctal<T>(ReadOnlySpan<byte> buffer) where T : struct, INumber<T>
         {
-            buffer = TrimEndingNullsAndSpaces(buffer);
-
             T octalFactor = T.CreateTruncating(8u);
             T value = T.Zero;
-            foreach (byte b in buffer)
+
+            // skip leading non-octal bytes
+            int offset = 0;
+            for (; offset < buffer.Length && (buffer[offset] < (byte)'0' || buffer[offset] > (byte)'7'); ++offset);
+
+            foreach (byte b in buffer.Slice(offset))
             {
-                uint digit = (uint)(b - '0');
-                if (digit >= 8)
-                {
-                    ThrowInvalidNumber();
-                }
+                if (b < (byte)'0' || b > (byte)'7') break;
 
-                value = checked((value * octalFactor) + T.CreateTruncating(digit));
+                value = checked((value * octalFactor) + T.CreateTruncating((uint)(b - '0')));
             }
 
             return value;
diff --git a/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.File.Tests.cs b/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.File.Tests.cs
index 5e35c12c3aaac9..75e3e27ef9e0fb 100644
--- a/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.File.Tests.cs
+++ b/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.File.Tests.cs
@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
@@ -125,28 +125,38 @@ public void Read_Archive_LongFileName_Over100_Under255(TarEntryFormat format, Te
         public void Read_Archive_LongPath_Over255(TarEntryFormat format, TestTarFormat testFormat) =>
             Read_Archive_LongPath_Over255_Internal(format, testFormat);
 
-        [Fact]
-        public void Read_NodeTarArchives_Successfully()
+        public static IEnumerable<object[]> GetTarFiles(string subset)
         {
-            string nodeTarPath = Path.Join(Directory.GetCurrentDirectory(), "tar", "node-tar");
-            foreach (string file in Directory.EnumerateFiles(nodeTarPath, "*.tar", SearchOption.AllDirectories))
+            string path = Path.Join(Directory.GetCurrentDirectory(), "tar", subset);
+            foreach (string file in Directory.EnumerateFiles(path, "*.tar", SearchOption.AllDirectories))
             {
-                using FileStream sourceStream = File.Open(file, FileMode.Open, FileAccess.Read, FileShare.Read);
-                using var reader = new TarReader(sourceStream);
+                yield return new object[] { file };
+            }
+        }
 
-                TarEntry? entry = null;
-                while (true)
-                {
-                    Exception ex = Record.Exception(() => entry = reader.GetNextEntry());
-                    Assert.Null(ex);
+        [Theory]
+        [MemberData(nameof(GetTarFiles), "node-tar")]
+        [MemberData(nameof(GetTarFiles), "tar-rs")]
+        public void Read_TestArchives_Successfully(string file)
+        {
+            using FileStream sourceStream = File.Open(file, FileMode.Open, FileAccess.Read, FileShare.Read);
+            using var reader = new TarReader(sourceStream);
 
-                    if (entry is null) break;
+            TarEntry? entry = null;
+            while ((entry = reader.GetNextEntry()) != null)
+            {
+                Assert.NotNull(entry.Name);
+                Assert.True(Enum.IsDefined(entry.EntryType));
+                Assert.True(Enum.IsDefined(entry.Format));
 
-                    ex = Record.Exception(() => entry.Name);
-                    Assert.Null(ex);
+                if (entry.EntryType == TarEntryType.Directory)
+                    continue;
 
-                    ex = Record.Exception(() => entry.Length);
-                    Assert.Null(ex);
+                var ds = entry.DataStream;
+                if (ds != null && ds.Length > 0)
+                {
+                    using var memoryStream = new MemoryStream();
+                    ds.CopyTo(memoryStream);
                 }
             }
         }
diff --git a/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntry.Tests.cs b/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntry.Tests.cs
index bad9bf8fa179bf..a1ab5e9ffdc521 100644
--- a/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntry.Tests.cs
+++ b/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntry.Tests.cs
@@ -20,19 +20,6 @@ public void MalformedArchive_TooSmall()
             Assert.Throws<EndOfStreamException>(() => reader.GetNextEntry());
         }
 
-        [Fact]
-        public void MalformedArchive_HeaderSize()
-        {
-            using MemoryStream malformed = new MemoryStream();
-            byte[] buffer = new byte[512]; // Minimum length of any header
-            Array.Fill<byte>(buffer, 0x1);
-            malformed.Write(buffer);
-            malformed.Seek(0, SeekOrigin.Begin);
-
-            using TarReader reader = new TarReader(malformed);
-            Assert.Throws<FormatException>(() => reader.GetNextEntry());
-        }
-
         [Fact]
         public void EmptyArchive()
         {
diff --git a/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntryAsync.Tests.cs b/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntryAsync.Tests.cs
index 77ddf1f1320621..fa21cad647dc33 100644
--- a/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntryAsync.Tests.cs
+++ b/src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntryAsync.Tests.cs
@@ -39,23 +39,6 @@ public async Task MalformedArchive_TooSmall_Async()
             }
         }
 
-        [Fact]
-        public async Task MalformedArchive_HeaderSize_Async()
-        {
-            await using (MemoryStream malformed = new MemoryStream())
-            {
-                byte[] buffer = new byte[512]; // Minimum length of any header
-                Array.Fill<byte>(buffer, 0x1);
-                malformed.Write(buffer);
-                malformed.Seek(0, SeekOrigin.Begin);
-
-                await using (TarReader reader = new TarReader(malformed))
-                {
-                    await Assert.ThrowsAsync<FormatException>(async () => await reader.GetNextEntryAsync());
-                }
-            }
-        }
-
         [Fact]
         public async Task EmptyArchive_Async()
         {