diff --git a/internal/controller/shardsplitjob_copy.go b/internal/controller/shardsplitjob_copy.go
index 44e0d42b..bc70f267 100644
--- a/internal/controller/shardsplitjob_copy.go
+++ b/internal/controller/shardsplitjob_copy.go
@@ -69,12 +69,15 @@ func sourceShardPodDNS(cluster, ns, shardID string) (string, error) {
 	if !strings.HasPrefix(shardID, "shard-") {
 		return "", fmt.Errorf("source shard %q is not ordinal (want shard-N)", shardID)
 	}
-	ord, err := strconv.Atoi(strings.TrimPrefix(shardID, "shard-"))
+
+	// bitSize 32 — int32 를 넘는 ordinal 은 잘려 다른 shard pod 를 가리키므로 거부한다.
+	v, err := strconv.ParseInt(strings.TrimPrefix(shardID, "shard-"), 10, 32)
 	if err != nil {
 		return "", fmt.Errorf("source shard %q: %w", shardID, err)
 	}
-	pod := ShardStatefulSetName(cluster, int32(ord)) + "-0"
-	return fmt.Sprintf("%s.%s.%s.svc.cluster.local", pod, ShardServiceName(cluster, int32(ord)), ns), nil
+	ord := int32(v)
+	pod := ShardStatefulSetName(cluster, ord) + "-0"
+	return fmt.Sprintf("%s.%s.%s.svc.cluster.local", pod, ShardServiceName(cluster, ord), ns), nil
 }
 
 // targetShardPodDNS 는 resharding target shard 의 primary pod(-0) 안정 DNS 를 만든다.
diff --git a/internal/controller/shardsplitjob_copy_bounds_test.go b/internal/controller/shardsplitjob_copy_bounds_test.go
new file mode 100644
index 00000000..28431bf9
--- /dev/null
+++ b/internal/controller/shardsplitjob_copy_bounds_test.go
@@ -0,0 +1,45 @@
+/*
+Copyright 2026 keiailab.
+
+Licensed under the MIT License. See the LICENSE file for details.
+*/
+
+package controller
+
+import (
+	"strings"
+	"testing"
+)
+
+// TestSourceShardPodDNS_OrdinalBounds 는 shard ordinal 이 int32 범위를 벗어나면
+// 잘라서 엉뚱한 pod 를 가리키지 않고 에러를 내는지 검증한다.
+func TestSourceShardPodDNS_OrdinalBounds(t *testing.T) {
+	tests := []struct {
+		shard   string
+		wantErr bool
+		wantPod string
+	}{
+		{shard: "shard-0", wantPod: "c-shard-0-0."},
+		{shard: "shard-2147483647", wantPod: "c-shard-2147483647-0."},
+		{shard: "shard-2147483648", wantErr: true},
+		{shard: "shard-4294967296", wantErr: true},
+		{shard: "shard-x", wantErr: true},
+		{shard: "s-1", wantErr: true},
+	}
+	for _, tt := range tests {
+		got, err := sourceShardPodDNS("c", "ns", tt.shard)
+		if tt.wantErr {
+			if err == nil {
+				t.Errorf("%s: want error, got %q", tt.shard, got)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", tt.shard, err)
+			continue
+		}
+		if !strings.HasPrefix(got, tt.wantPod) {
+			t.Errorf("%s: got %q, want prefix %q", tt.shard, got, tt.wantPod)
+		}
+	}
+}
diff --git a/internal/router/vindex.go b/internal/router/vindex.go
index 4223b764..40a63e38 100644
--- a/internal/router/vindex.go
+++ b/internal/router/vindex.go
@@ -108,11 +108,12 @@ func hashKey(fn v1alpha1.VindexHashFunction, key string) (uint32, error) {
 }
 
 // parseHashBound 는 hex 문자열 ("0x..." 또는 "ffffffff") 또는 10진수를 uint32 로 해석한다.
+// uint32 를 넘는 값은 잘려 다른 범위가 되므로 bitSize 32 로 거부한다.
 func parseHashBound(s string) (uint32, error) {
-	if v, err := strconv.ParseUint(s, 0, 64); err == nil {
+	if v, err := strconv.ParseUint(s, 0, 32); err == nil {
 		return uint32(v), nil
 	}
-	if v, err := strconv.ParseUint(s, 16, 64); err == nil {
+	if v, err := strconv.ParseUint(s, 16, 32); err == nil {
 		return uint32(v), nil
 	}
 	return 0, fmt.Errorf("invalid hash bound %q (expected hex or decimal)", s)
diff --git a/internal/router/vindex_bound_test.go b/internal/router/vindex_bound_test.go
new file mode 100644
index 00000000..1cc1675d
--- /dev/null
+++ b/internal/router/vindex_bound_test.go
@@ -0,0 +1,46 @@
+/*
+Copyright 2026 keiailab.
+
+Licensed under the MIT License. See the LICENSE file for details.
+*/
+
+package router
+
+import "testing"
+
+// TestParseHashBound_Bounds 는 uint32 를 넘는 bound 를 잘라 엉뚱한 범위로
+// 해석하지 않고 에러를 내는지 검증한다 (예: 0x100000000 → 0 이 되면 안 된다).
+func TestParseHashBound_Bounds(t *testing.T) {
+	tests := []struct {
+		in      string
+		want    uint32
+		wantErr bool
+	}{
+		{in: "0", want: 0},
+		{in: "0x00000000", want: 0},
+		{in: "0xffffffff", want: 0xffffffff},
+		{in: "ffffffff", want: 0xffffffff},
+		{in: "4294967295", want: 0xffffffff},
+		{in: "4294967296", wantErr: true},
+		{in: "0x100000000", wantErr: true},
+		{in: "100000000f", wantErr: true},
+		{in: "-1", wantErr: true},
+		{in: "zz", wantErr: true},
+	}
+	for _, tt := range tests {
+		got, err := parseHashBound(tt.in)
+		if tt.wantErr {
+			if err == nil {
+				t.Errorf("%q: want error, got %#x", tt.in, got)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("%q: unexpected error: %v", tt.in, err)
+			continue
+		}
+		if got != tt.want {
+			t.Errorf("%q: got %#x, want %#x", tt.in, got, tt.want)
+		}
+	}
+}