2 files changed, 8 insertions, 2 deletions
diff --git a/crypto/src/math/ec/ECAlgorithms.cs b/crypto/src/math/ec/ECAlgorithms.cs
index fcfab06f7..3059ca3b3 100644
--- a/crypto/src/math/ec/ECAlgorithms.cs
+++ b/crypto/src/math/ec/ECAlgorithms.cs
@@ -216,7 +216,10 @@ namespace Org.BouncyCastle.Math.EC
                 throw new ArgumentException("Point must be on the same curve", nameof(p));
 
 #if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
-            Span<byte> encoding = stackalloc byte[p.GetEncodedLength(false)];
+            int encodedLength = p.GetEncodedLength(false);
+            Span<byte> encoding = encodedLength <= 512
+                ? stackalloc byte[encodedLength]
+                : new byte[encodedLength];
             p.EncodeTo(false, encoding);
             return c.DecodePoint(encoding);
 #else
diff --git a/crypto/src/math/ec/rfc8032/Ed25519.cs b/crypto/src/math/ec/rfc8032/Ed25519.cs
index d6bf461cf..f3b63f3b3 100644
--- a/crypto/src/math/ec/rfc8032/Ed25519.cs
+++ b/crypto/src/math/ec/rfc8032/Ed25519.cs
@@ -433,7 +433,10 @@ namespace Org.BouncyCastle.Math.EC.Rfc8032
         public static void GeneratePublicKey(ReadOnlySpan<byte> sk, Span<byte> pk)
         {
             IDigest d = CreateDigest();
-            Span<byte> h = stackalloc byte[d.GetDigestSize()];
+            int digestSize = d.GetDigestSize();
+            Span<byte> h = digestSize <= 128
+                ? stackalloc byte[digestSize]
+                : new byte[digestSize];
 
             d.BlockUpdate(sk[..SecretKeySize]);
             d.DoFinal(h);