diff --git a/weed/s3api/s3api_object_handlers_put.go b/weed/s3api/s3api_object_handlers_put.go
index d1b2da9e4..d666df096 100644
--- a/weed/s3api/s3api_object_handlers_put.go
+++ b/weed/s3api/s3api_object_handlers_put.go
@@ -419,16 +419,51 @@ func (s3a *S3ApiServer) putToFiler(r *http.Request, uploadUrl string, dataReader
 			}
 		}
 	} else if sseKMSKey != nil {
-		// SSE-KMS: Store serialized metadata in all chunks
+		// SSE-KMS: Create per-chunk metadata with chunk-specific offsets
+		// Each chunk needs its own metadata with ChunkOffset set for proper IV calculation during decryption
 		for _, chunk := range chunkResult.FileChunks {
 			chunk.SseType = filer_pb.SSEType_SSE_KMS
-			chunk.SseMetadata = sseKMSMetadata
+			
+			// Create a copy of the SSE-KMS key with chunk-specific offset
+			chunkSSEKey := &SSEKMSKey{
+				KeyID:             sseKMSKey.KeyID,
+				EncryptedDataKey:  sseKMSKey.EncryptedDataKey,
+				EncryptionContext: sseKMSKey.EncryptionContext,
+				BucketKeyEnabled:  sseKMSKey.BucketKeyEnabled,
+				IV:                sseKMSKey.IV,
+				ChunkOffset:       chunk.Offset, // Set chunk-specific offset for IV calculation
+			}
+			
+			// Serialize per-chunk metadata
+			if chunkMetadata, serErr := SerializeSSEKMSMetadata(chunkSSEKey); serErr == nil {
+				chunk.SseMetadata = chunkMetadata
+			} else {
+				glog.Errorf("Failed to serialize SSE-KMS metadata for chunk at offset %d: %v", chunk.Offset, serErr)
+			}
 		}
 	} else if sseS3Key != nil {
-		// SSE-S3: Store serialized metadata in all chunks
+		// SSE-S3: Create per-chunk metadata with chunk-specific IVs
+		// Each chunk needs its own IV calculated from the base IV + chunk offset
 		for _, chunk := range chunkResult.FileChunks {
 			chunk.SseType = filer_pb.SSEType_SSE_S3
-			chunk.SseMetadata = sseS3Metadata
+			
+			// Calculate chunk-specific IV using base IV and chunk offset
+			chunkIV, _ := calculateIVWithOffset(sseS3Key.IV, chunk.Offset)
+			
+			// Create a copy of the SSE-S3 key with chunk-specific IV
+			chunkSSEKey := &SSES3Key{
+				Key:       sseS3Key.Key,
+				KeyID:     sseS3Key.KeyID,
+				Algorithm: sseS3Key.Algorithm,
+				IV:        chunkIV, // Use chunk-specific IV
+			}
+			
+			// Serialize per-chunk metadata
+			if chunkMetadata, serErr := SerializeSSES3Metadata(chunkSSEKey); serErr == nil {
+				chunk.SseMetadata = chunkMetadata
+			} else {
+				glog.Errorf("Failed to serialize SSE-S3 metadata for chunk at offset %d: %v", chunk.Offset, serErr)
+			}
 		}
 	}
 
diff --git a/weed/s3api/s3api_sse_chunk_metadata_test.go b/weed/s3api/s3api_sse_chunk_metadata_test.go
new file mode 100644
index 000000000..d02502249
--- /dev/null
+++ b/weed/s3api/s3api_sse_chunk_metadata_test.go
@@ -0,0 +1,362 @@
+package s3api
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/json"
+	"io"
+	"testing"
+
+	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
+)
+
+// TestSSEKMSChunkMetadataAssignment tests that SSE-KMS creates per-chunk metadata
+// with correct ChunkOffset values for each chunk (matching the fix in putToFiler)
+func TestSSEKMSChunkMetadataAssignment(t *testing.T) {
+	kmsKey := SetupTestKMS(t)
+	defer kmsKey.Cleanup()
+
+	// Generate SSE-KMS key by encrypting test data (this gives us a real SSEKMSKey)
+	encryptionContext := BuildEncryptionContext("test-bucket", "test-object", false)
+	testData := "Test data for SSE-KMS chunk metadata validation"
+	encryptedReader, sseKMSKey, err := CreateSSEKMSEncryptedReader(bytes.NewReader([]byte(testData)), kmsKey.KeyID, encryptionContext)
+	if err != nil {
+		t.Fatalf("Failed to create encrypted reader: %v", err)
+	}
+	// Read to complete encryption setup
+	io.ReadAll(encryptedReader)
+
+	// Serialize the base metadata (what putToFiler receives before chunking)
+	baseMetadata, err := SerializeSSEKMSMetadata(sseKMSKey)
+	if err != nil {
+		t.Fatalf("Failed to serialize base SSE-KMS metadata: %v", err)
+	}
+
+	// Simulate multi-chunk upload scenario (what putToFiler does after UploadReaderInChunks)
+	simulatedChunks := []*filer_pb.FileChunk{
+		{FileId: "chunk1", Offset: 0, Size: 8 * 1024 * 1024},        // 8MB chunk at offset 0
+		{FileId: "chunk2", Offset: 8 * 1024 * 1024, Size: 8 * 1024 * 1024}, // 8MB chunk at offset 8MB
+		{FileId: "chunk3", Offset: 16 * 1024 * 1024, Size: 4 * 1024 * 1024}, // 4MB chunk at offset 16MB
+	}
+
+	// THIS IS THE CRITICAL FIX: Create per-chunk metadata (lines 421-443 in putToFiler)
+	for _, chunk := range simulatedChunks {
+		chunk.SseType = filer_pb.SSEType_SSE_KMS
+
+		// Create a copy of the SSE-KMS key with chunk-specific offset
+		chunkSSEKey := &SSEKMSKey{
+			KeyID:             sseKMSKey.KeyID,
+			EncryptedDataKey:  sseKMSKey.EncryptedDataKey,
+			EncryptionContext: sseKMSKey.EncryptionContext,
+			BucketKeyEnabled:  sseKMSKey.BucketKeyEnabled,
+			IV:                sseKMSKey.IV,
+			ChunkOffset:       chunk.Offset, // Set chunk-specific offset
+		}
+
+		// Serialize per-chunk metadata
+		chunkMetadata, serErr := SerializeSSEKMSMetadata(chunkSSEKey)
+		if serErr != nil {
+			t.Fatalf("Failed to serialize SSE-KMS metadata for chunk at offset %d: %v", chunk.Offset, serErr)
+		}
+		chunk.SseMetadata = chunkMetadata
+	}
+
+	// VERIFICATION 1: Each chunk should have different metadata (due to different ChunkOffset)
+	metadataSet := make(map[string]bool)
+	for i, chunk := range simulatedChunks {
+		metadataStr := string(chunk.SseMetadata)
+		if metadataSet[metadataStr] {
+			t.Errorf("Chunk %d has duplicate metadata (should be unique per chunk)", i)
+		}
+		metadataSet[metadataStr] = true
+
+		// Deserialize and verify ChunkOffset
+		var metadata SSEKMSMetadata
+		if err := json.Unmarshal(chunk.SseMetadata, &metadata); err != nil {
+			t.Fatalf("Failed to deserialize chunk %d metadata: %v", i, err)
+		}
+
+		expectedOffset := chunk.Offset
+		if metadata.PartOffset != expectedOffset {
+			t.Errorf("Chunk %d: expected PartOffset=%d, got %d", i, expectedOffset, metadata.PartOffset)
+		}
+
+		t.Logf("✓ Chunk %d: PartOffset=%d (correct)", i, metadata.PartOffset)
+	}
+
+	// VERIFICATION 2: Verify metadata can be deserialized and has correct ChunkOffset
+	for i, chunk := range simulatedChunks {
+		// Deserialize chunk metadata
+		deserializedKey, err := DeserializeSSEKMSMetadata(chunk.SseMetadata)
+		if err != nil {
+			t.Fatalf("Failed to deserialize chunk %d metadata: %v", i, err)
+		}
+
+		// Verify the deserialized key has correct ChunkOffset
+		if deserializedKey.ChunkOffset != chunk.Offset {
+			t.Errorf("Chunk %d: deserialized ChunkOffset=%d, expected %d",
+				i, deserializedKey.ChunkOffset, chunk.Offset)
+		}
+
+		// Verify IV is set (should be inherited from base)
+		if len(deserializedKey.IV) != aes.BlockSize {
+			t.Errorf("Chunk %d: invalid IV length: %d", i, len(deserializedKey.IV))
+		}
+
+		// Verify KeyID matches
+		if deserializedKey.KeyID != sseKMSKey.KeyID {
+			t.Errorf("Chunk %d: KeyID mismatch", i)
+		}
+
+		t.Logf("✓ Chunk %d: metadata deserialized successfully (ChunkOffset=%d, KeyID=%s)", 
+			i, deserializedKey.ChunkOffset, deserializedKey.KeyID)
+	}
+
+	// VERIFICATION 3: Ensure base metadata is NOT reused (the bug we're preventing)
+	var baseMetadataStruct SSEKMSMetadata
+	if err := json.Unmarshal(baseMetadata, &baseMetadataStruct); err != nil {
+		t.Fatalf("Failed to deserialize base metadata: %v", err)
+	}
+
+	// Base metadata should have ChunkOffset=0
+	if baseMetadataStruct.PartOffset != 0 {
+		t.Errorf("Base metadata should have PartOffset=0, got %d", baseMetadataStruct.PartOffset)
+	}
+
+	// Chunks 2 and 3 should NOT have the same metadata as base (proving we're not reusing)
+	for i := 1; i < len(simulatedChunks); i++ {
+		if bytes.Equal(simulatedChunks[i].SseMetadata, baseMetadata) {
+			t.Errorf("CRITICAL BUG: Chunk %d reuses base metadata (should have per-chunk metadata)", i)
+		}
+	}
+
+	t.Log("✓ All chunks have unique per-chunk metadata (bug prevented)")
+}
+
+// TestSSES3ChunkMetadataAssignment tests that SSE-S3 creates per-chunk metadata
+// with offset-adjusted IVs for each chunk (matching the fix in putToFiler)
+func TestSSES3ChunkMetadataAssignment(t *testing.T) {
+	// Initialize global SSE-S3 key manager
+	globalSSES3KeyManager = NewSSES3KeyManager()
+	defer func() {
+		globalSSES3KeyManager = NewSSES3KeyManager()
+	}()
+
+	keyManager := GetSSES3KeyManager()
+	keyManager.superKey = make([]byte, 32)
+	rand.Read(keyManager.superKey)
+
+	// Generate SSE-S3 key
+	sseS3Key, err := GenerateSSES3Key()
+	if err != nil {
+		t.Fatalf("Failed to generate SSE-S3 key: %v", err)
+	}
+
+	// Generate base IV
+	baseIV := make([]byte, aes.BlockSize)
+	rand.Read(baseIV)
+	sseS3Key.IV = baseIV
+
+	// Serialize base metadata (what putToFiler receives)
+	baseMetadata, err := SerializeSSES3Metadata(sseS3Key)
+	if err != nil {
+		t.Fatalf("Failed to serialize base SSE-S3 metadata: %v", err)
+	}
+
+	// Simulate multi-chunk upload scenario (what putToFiler does after UploadReaderInChunks)
+	simulatedChunks := []*filer_pb.FileChunk{
+		{FileId: "chunk1", Offset: 0, Size: 8 * 1024 * 1024},        // 8MB chunk at offset 0
+		{FileId: "chunk2", Offset: 8 * 1024 * 1024, Size: 8 * 1024 * 1024}, // 8MB chunk at offset 8MB
+		{FileId: "chunk3", Offset: 16 * 1024 * 1024, Size: 4 * 1024 * 1024}, // 4MB chunk at offset 16MB
+	}
+
+	// THIS IS THE CRITICAL FIX: Create per-chunk metadata (lines 444-468 in putToFiler)
+	for _, chunk := range simulatedChunks {
+		chunk.SseType = filer_pb.SSEType_SSE_S3
+
+		// Calculate chunk-specific IV using base IV and chunk offset
+		chunkIV, _ := calculateIVWithOffset(sseS3Key.IV, chunk.Offset)
+
+		// Create a copy of the SSE-S3 key with chunk-specific IV
+		chunkSSEKey := &SSES3Key{
+			Key:       sseS3Key.Key,
+			KeyID:     sseS3Key.KeyID,
+			Algorithm: sseS3Key.Algorithm,
+			IV:        chunkIV, // Use chunk-specific IV
+		}
+
+		// Serialize per-chunk metadata
+		chunkMetadata, serErr := SerializeSSES3Metadata(chunkSSEKey)
+		if serErr != nil {
+			t.Fatalf("Failed to serialize SSE-S3 metadata for chunk at offset %d: %v", chunk.Offset, serErr)
+		}
+		chunk.SseMetadata = chunkMetadata
+	}
+
+	// VERIFICATION 1: Each chunk should have different metadata (due to different IVs)
+	metadataSet := make(map[string]bool)
+	for i, chunk := range simulatedChunks {
+		metadataStr := string(chunk.SseMetadata)
+		if metadataSet[metadataStr] {
+			t.Errorf("Chunk %d has duplicate metadata (should be unique per chunk)", i)
+		}
+		metadataSet[metadataStr] = true
+
+		// Deserialize and verify IV
+		deserializedKey, err := DeserializeSSES3Metadata(chunk.SseMetadata, keyManager)
+		if err != nil {
+			t.Fatalf("Failed to deserialize chunk %d metadata: %v", i, err)
+		}
+
+		// Calculate expected IV for this chunk
+		expectedIV, _ := calculateIVWithOffset(baseIV, chunk.Offset)
+		if !bytes.Equal(deserializedKey.IV, expectedIV) {
+			t.Errorf("Chunk %d: IV mismatch\nExpected: %x\nGot: %x",
+				i, expectedIV[:8], deserializedKey.IV[:8])
+		}
+
+		t.Logf("✓ Chunk %d: IV correctly adjusted for offset=%d", i, chunk.Offset)
+	}
+
+	// VERIFICATION 2: Verify decryption works with per-chunk IVs
+	for i, chunk := range simulatedChunks {
+		// Deserialize chunk metadata
+		deserializedKey, err := DeserializeSSES3Metadata(chunk.SseMetadata, keyManager)
+		if err != nil {
+			t.Fatalf("Failed to deserialize chunk %d metadata: %v", i, err)
+		}
+
+		// Simulate encryption/decryption with the chunk's IV
+		testData := []byte("Test data for SSE-S3 chunk decryption verification")
+		block, err := aes.NewCipher(deserializedKey.Key)
+		if err != nil {
+			t.Fatalf("Failed to create cipher: %v", err)
+		}
+
+		// Encrypt with chunk's IV
+		ciphertext := make([]byte, len(testData))
+		stream := cipher.NewCTR(block, deserializedKey.IV)
+		stream.XORKeyStream(ciphertext, testData)
+
+		// Decrypt with chunk's IV
+		plaintext := make([]byte, len(ciphertext))
+		block2, _ := aes.NewCipher(deserializedKey.Key)
+		stream2 := cipher.NewCTR(block2, deserializedKey.IV)
+		stream2.XORKeyStream(plaintext, ciphertext)
+
+		if !bytes.Equal(plaintext, testData) {
+			t.Errorf("Chunk %d: decryption failed", i)
+		}
+
+		t.Logf("✓ Chunk %d: encryption/decryption successful with chunk-specific IV", i)
+	}
+
+	// VERIFICATION 3: Ensure base IV is NOT reused for non-zero offset chunks (the bug we're preventing)
+	for i := 1; i < len(simulatedChunks); i++ {
+		if bytes.Equal(simulatedChunks[i].SseMetadata, baseMetadata) {
+			t.Errorf("CRITICAL BUG: Chunk %d reuses base metadata (should have per-chunk metadata)", i)
+		}
+
+		// Verify chunk metadata has different IV than base IV
+		deserializedKey, _ := DeserializeSSES3Metadata(simulatedChunks[i].SseMetadata, keyManager)
+		if bytes.Equal(deserializedKey.IV, baseIV) {
+			t.Errorf("CRITICAL BUG: Chunk %d uses base IV (should use offset-adjusted IV)", i)
+		}
+	}
+
+	t.Log("✓ All chunks have unique per-chunk IVs (bug prevented)")
+}
+
+// TestSSEChunkMetadataComparison tests that the bug (reusing same metadata for all chunks)
+// would cause decryption failures, while the fix (per-chunk metadata) works correctly
+func TestSSEChunkMetadataComparison(t *testing.T) {
+	// Generate test key and IV
+	key := make([]byte, 32)
+	rand.Read(key)
+	baseIV := make([]byte, aes.BlockSize)
+	rand.Read(baseIV)
+
+	// Create test data for 3 chunks
+	chunk0Data := []byte("Chunk 0 data at offset 0")
+	chunk1Data := []byte("Chunk 1 data at offset 8MB")
+	chunk2Data := []byte("Chunk 2 data at offset 16MB")
+
+	chunkOffsets := []int64{0, 8 * 1024 * 1024, 16 * 1024 * 1024}
+	chunkDataList := [][]byte{chunk0Data, chunk1Data, chunk2Data}
+
+	// Scenario 1: BUG - Using same IV for all chunks (what the old code did)
+	t.Run("Bug: Reusing base IV causes decryption failures", func(t *testing.T) {
+		var encryptedChunks [][]byte
+
+		// Encrypt each chunk with offset-adjusted IV (what encryption does)
+		for i, offset := range chunkOffsets {
+			adjustedIV, _ := calculateIVWithOffset(baseIV, offset)
+			block, _ := aes.NewCipher(key)
+			stream := cipher.NewCTR(block, adjustedIV)
+
+			ciphertext := make([]byte, len(chunkDataList[i]))
+			stream.XORKeyStream(ciphertext, chunkDataList[i])
+			encryptedChunks = append(encryptedChunks, ciphertext)
+		}
+
+		// Try to decrypt with base IV (THE BUG)
+		for i := range encryptedChunks {
+			block, _ := aes.NewCipher(key)
+			stream := cipher.NewCTR(block, baseIV) // BUG: Always using base IV
+
+			plaintext := make([]byte, len(encryptedChunks[i]))
+			stream.XORKeyStream(plaintext, encryptedChunks[i])
+
+			if i == 0 {
+				// Chunk 0 should work (offset 0 means base IV = adjusted IV)
+				if !bytes.Equal(plaintext, chunkDataList[i]) {
+					t.Errorf("Chunk 0 decryption failed (unexpected)")
+				}
+			} else {
+				// Chunks 1 and 2 should FAIL (wrong IV)
+				if bytes.Equal(plaintext, chunkDataList[i]) {
+					t.Errorf("BUG NOT REPRODUCED: Chunk %d decrypted correctly with base IV (should fail)", i)
+				} else {
+					t.Logf("✓ Chunk %d: Correctly failed to decrypt with base IV (bug reproduced)", i)
+				}
+			}
+		}
+	})
+
+	// Scenario 2: FIX - Using per-chunk offset-adjusted IVs (what the new code does)
+	t.Run("Fix: Per-chunk IVs enable correct decryption", func(t *testing.T) {
+		var encryptedChunks [][]byte
+		var chunkIVs [][]byte
+
+		// Encrypt each chunk with offset-adjusted IV
+		for i, offset := range chunkOffsets {
+			adjustedIV, _ := calculateIVWithOffset(baseIV, offset)
+			chunkIVs = append(chunkIVs, adjustedIV)
+
+			block, _ := aes.NewCipher(key)
+			stream := cipher.NewCTR(block, adjustedIV)
+
+			ciphertext := make([]byte, len(chunkDataList[i]))
+			stream.XORKeyStream(ciphertext, chunkDataList[i])
+			encryptedChunks = append(encryptedChunks, ciphertext)
+		}
+
+		// Decrypt with per-chunk IVs (THE FIX)
+		for i := range encryptedChunks {
+			block, _ := aes.NewCipher(key)
+			stream := cipher.NewCTR(block, chunkIVs[i]) // FIX: Using per-chunk IV
+
+			plaintext := make([]byte, len(encryptedChunks[i]))
+			stream.XORKeyStream(plaintext, encryptedChunks[i])
+
+			if !bytes.Equal(plaintext, chunkDataList[i]) {
+				t.Errorf("Chunk %d decryption failed with per-chunk IV (unexpected)", i)
+			} else {
+				t.Logf("✓ Chunk %d: Successfully decrypted with per-chunk IV", i)
+			}
+		}
+	})
+}
+