diff --git a/Source/astcenc_block_sizes.cpp b/Source/astcenc_block_sizes.cpp
index e7b5348aa0b65c0731d0b20418af4adaa3490ca4..0093bf55d9b04fbb2a299aa50db88918f09cc85b 100644
--- a/Source/astcenc_block_sizes.cpp
+++ b/Source/astcenc_block_sizes.cpp
@@ -821,6 +821,12 @@ static void construct_block_size_descriptor_2d(
 	// Gather all the decimation grids that can be used with the current block
 #if !defined(ASTCENC_DECOMPRESS_ONLY)
 	const float *percentiles = get_2d_percentile_table(x_texels, y_texels);
+    if (percentiles == nullptr) {
+        delete wb;
+#ifdef ASTC_CUSTOMIZED_ENABLE
+        return false;
+#endif
+    }
 	float always_cutoff = (privateProfile != HIGH_QUALITY_PROFILE) ? 1.0f : 0.0f;
 #else
 	// Unused in decompress-only builds
diff --git a/Source/astcenc_color_quantize.cpp b/Source/astcenc_color_quantize.cpp
index 4ac0aff58dcc72aa9f93f6f92f56400c30b0209b..7b61a7ccd53823ed2cc4de523a0919ee0b200ae1 100644
--- a/Source/astcenc_color_quantize.cpp
+++ b/Source/astcenc_color_quantize.cpp
@@ -73,6 +73,7 @@ static inline uint8_t quant_color(
 	quant_method quant_level,
 	int value
 ) {
+    value = astc::clamp(value, 0, 255); // 255: maximum value
 	int index = value * 2 + 1;
 	return color_unquant_to_uquant_tables[quant_level - QUANT_6][index];
 }
diff --git a/Source/astcenc_percentile_tables.cpp b/Source/astcenc_percentile_tables.cpp
index 448ddcc968e0dbac52b221329294871e36ed3b55..98f5777566aa006c9be3190b2492687877bd9354 100644
--- a/Source/astcenc_percentile_tables.cpp
+++ b/Source/astcenc_percentile_tables.cpp
@@ -1168,6 +1168,10 @@ const float *get_2d_percentile_table(
 ) {
 	float* unpacked_table = new float[WEIGHTS_MAX_BLOCK_MODES];
 	const packed_percentile_table *apt = get_packed_table(xdim, ydim);
+    if (apt == nullptr) {
+        delete[] unpacked_table;
+        return nullptr;
+    }
 
 	// Set the default percentile
 	for (unsigned int i = 0; i < WEIGHTS_MAX_BLOCK_MODES; i++)
diff --git a/Source/astcenc_pick_best_endpoint_format.cpp b/Source/astcenc_pick_best_endpoint_format.cpp
index d3b9f6c296efe2857e9ecfc941d9a59606e1c0e0..2b97bd95c5efe7e46a9cee78a9bea3cd94251455 100644
--- a/Source/astcenc_pick_best_endpoint_format.cpp
+++ b/Source/astcenc_pick_best_endpoint_format.cpp
@@ -917,6 +917,9 @@ static float two_partitions_find_best_combination_for_bitcount(
 
 	if (ql >= QUANT_6)
 	{
+        if (best_integer_count < 2) { // 2: minimum integer_count
+            return ERROR_CALC_DEFAULT;
+        }
 		for (int i = 0; i < 2; i++)
 		{
 			best_formats[i] = best_combined_format[ql][best_integer_count - 2][i];
@@ -1042,6 +1045,9 @@ static float three_partitions_find_best_combination_for_bitcount(
 
 	if (ql >= QUANT_6)
 	{
+        if (best_integer_count < 3) { // 3: minimum integer_count
+            return ERROR_CALC_DEFAULT;
+        }
 		for (int i = 0; i < 3; i++)
 		{
 			best_formats[i] = best_combined_format[ql][best_integer_count - 3][i];
@@ -1178,6 +1184,9 @@ static float four_partitions_find_best_combination_for_bitcount(
 
 	if (ql >= QUANT_6)
 	{
+        if (best_integer_count < 4) { // 4: minimum integer_count
+            return ERROR_CALC_DEFAULT;
+        }
 		for (int i = 0; i < 4; i++)
 		{
 			best_formats[i] = best_combined_format[ql][best_integer_count - 4][i];