diff --git a/smx509/sec1.go b/smx509/sec1.go
index 1d8b441..5e75e46 100644
--- a/smx509/sec1.go
+++ b/smx509/sec1.go
@@ -64,6 +64,9 @@ func MarshalSM2PrivateKey(key *sm2.PrivateKey) ([]byte, error) {
 // marshalECPrivateKey marshals an EC private key into ASN.1, DER format and
 // sets the curve ID to the given OID, or omits it if OID is nil.
 func marshalECPrivateKeyWithOID(key *ecdsa.PrivateKey, oid asn1.ObjectIdentifier) ([]byte, error) {
+	if !key.Curve.IsOnCurve(key.X, key.Y) {
+		return nil, errors.New("invalid elliptic key public key")
+	}
 	privateKey := make([]byte, (key.Curve.Params().N.BitLen()+7)/8)
 	return asn1.Marshal(ecPrivateKey{
 		Version:       1,
diff --git a/smx509/x509.go b/smx509/x509.go
index b873e01..51b515c 100644
--- a/smx509/x509.go
+++ b/smx509/x509.go
@@ -75,11 +75,14 @@ func marshalPublicKey(pub interface{}) (publicKeyBytes []byte, publicKeyAlgorith
 		// RFC 3279, Section 2.3.1.
 		publicKeyAlgorithm.Parameters = asn1.NullRawValue
 	case *ecdsa.PublicKey:
-		publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
 		oid, ok := oidFromNamedCurve(pub.Curve)
 		if !ok {
 			return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported elliptic curve")
 		}
+		if !pub.Curve.IsOnCurve(pub.X, pub.Y) {
+			return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: invalid elliptic curve public key")
+		}
+		publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
 		publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
 		var paramBytes []byte
 		paramBytes, err = asn1.Marshal(oid)
diff --git a/smx509/x509_test.go b/smx509/x509_test.go
index d63e4a6..b0d4c77 100644
--- a/smx509/x509_test.go
+++ b/smx509/x509_test.go
@@ -3104,3 +3104,17 @@ func TestDuplicateExtensionsCSR(t *testing.T) {
 		t.Fatal("ParseCertificate should fail when parsing certificate with duplicate extensions")
 	}
 }
+
+func TestMarshalInvalidPublicKey(t *testing.T) {
+	_, err := MarshalPKIXPublicKey(&ecdsa.PublicKey{})
+	if err == nil {
+		t.Errorf("expected error, got MarshalPKIXPublicKey success")
+	}
+	_, err = MarshalPKIXPublicKey(&ecdsa.PublicKey{
+		Curve: elliptic.P256(),
+		X:     big.NewInt(1), Y: big.NewInt(2),
+	})
+	if err == nil {
+		t.Errorf("expected error, got MarshalPKIXPublicKey success")
+	}
+}