diff --git a/tensorflow_text/core/kernels/sentencepiece/BUILD b/tensorflow_text/core/kernels/sentencepiece/BUILD
index 78e1eb8fd..20e5c8878 100644
--- a/tensorflow_text/core/kernels/sentencepiece/BUILD
+++ b/tensorflow_text/core/kernels/sentencepiece/BUILD
@@ -140,7 +140,6 @@ cc_library(
         "optimized_encoder.h",
     ],
     deps = [
-        ":config",
         ":double_array_trie",
         ":encoder_config",
     ],
@@ -198,7 +197,7 @@ tf_cc_library(
     deps = [
         ":optimized_decoder",
         ":sentencepiece_detokenizer_h",
-        # tf/protobuf:error_codes_proto_impl_cc tensorflow dep,
+        "@com_google_absl//absl/status",
     ],
 )
 
diff --git a/tensorflow_text/core/kernels/sentencepiece/optimized_encoder.cc b/tensorflow_text/core/kernels/sentencepiece/optimized_encoder.cc
index 9602684d0..fee0a6ef2 100644
--- a/tensorflow_text/core/kernels/sentencepiece/optimized_encoder.cc
+++ b/tensorflow_text/core/kernels/sentencepiece/optimized_encoder.cc
@@ -95,6 +95,9 @@ std::tuple<int, utils::string_view> find_replacement(
     const flatbuffers::Vector<int8_t>& replacements) {
   const auto max_match = dat.LongestPrefixMatch(utils::string_view(data, len));
   if (!max_match.empty()) {
+    if (max_match.id < 0 || max_match.id >= replacements.size()) {
+      return std::make_tuple(0, utils::string_view(nullptr, 0));
+    }
     // Because flatbuffer byte is signed char which is not the same as char,
     // there is the reinterpret_cast here.
     const char* replaced_string_ptr =
@@ -195,6 +198,9 @@ EncoderResult EncodeNormalizedString(const std::string& str,
     }
     auto lattice_update = [&lattice, i,
                            piece_scores](const DoubleArrayTrie::Match& m) {
+      if (m.id < 0 || m.id >= piece_scores->size()) {
+        return;
+      }
       LatticeElement& target_element = lattice[i + m.match_length];
       const float score = lattice[i].score + (*piece_scores)[m.id];
       if (target_element.prev_position < 0 || target_element.score < score) {
diff --git a/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_kernel.cc b/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_kernel.cc
index 3338ca38e..7e35041f6 100644
--- a/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_kernel.cc
+++ b/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_kernel.cc
@@ -32,6 +32,7 @@ limitations under the License.
 #include "tensorflow/core/framework/shape_inference.h"
 #include "tensorflow/core/framework/tensor.h"
 #include "tensorflow/core/platform/errors.h"
+#include "tensorflow/core/framework/op_requires.h"
 #include "tensorflow_text/core/kernels/sentencepiece/optimized_decoder.h"
 #include "tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer.h"
 
@@ -60,6 +61,12 @@ class TFSentencepieceDetokenizerOp : public tensorflow::OpKernel {
     for (int i = 0; i < num_of_sentences; i++) {
       // Create a vector of int32 from input according to spans.
       const int split_size = input_splits_flat(i + 1) - input_splits_flat(i);
+      OP_REQUIRES(
+          ctx,
+          split_size >= 0 &&
+              (input_offset + split_size) <= input_values_flat.size(),
+          errors::InvalidArgument("input_splits must be monotonically "
+                                  "non-decreasing and within bounds."));
       codes_for_split.clear();
       codes_for_split.reserve(split_size);
       for (int j = 0; j < split_size; ++j) {
diff --git a/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_tflite.cc b/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_tflite.cc
index 89e8a4723..3f8f6df4d 100644
--- a/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_tflite.cc
+++ b/tensorflow_text/core/kernels/sentencepiece/sentencepiece_detokenizer_tflite.cc
@@ -85,6 +85,12 @@ TfLiteStatus Eval(TfLiteContext* context, TfLiteNode* node) {
   for (int i = 0; i < num_of_sentences; i++) {
     // Create a vector of int32 from input according to spans.
     const int split_size = input_splits_data[i + 1] - input_splits_data[i];
+    TF_LITE_ENSURE_MSG(
+        context,
+        split_size >= 0 &&
+            (input_offset + split_size) <= NumElements(input_encoded.dims),
+        "input_splits must be monotonically non-decreasing and "
+        "within bounds.");
     codes_for_split.clear();
     std::copy(input_encoded_data + input_offset,
               input_encoded_data + input_offset + split_size,