diff --git a/es2panda/test/parser/js/test_ansi_string-expected.txt b/es2panda/test/parser/js/test_ansi_string-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..e5feefc5fe84096908752547fdfdbcb0a0fc0eb1
--- /dev/null
+++ b/es2panda/test/parser/js/test_ansi_string-expected.txt
@@ -0,0 +1 @@
+SyntaxError: Unterminated RegExp [test_unsafe_file.js:16:7]
diff --git a/es2panda/test/parser/js/test_ansi_string.js b/es2panda/test/parser/js/test_ansi_string.js
new file mode 100644
index 0000000000000000000000000000000000000000..6ee51d23286af3bd30bbb6fd82aa5633d9779d83
--- /dev/null
+++ b/es2panda/test/parser/js/test_ansi_string.js
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2024 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/ ��?\������? ??\+ ??\/ ??\/ ??\
diff --git a/es2panda/util/ustring.h b/es2panda/util/ustring.h
index 52976ee8acabd2c235cb2bafb73229d6c880a2ed..94c36ac06a5f0e8e54e75cb4967d0e8b6eac054e 100644
--- a/es2panda/util/ustring.h
+++ b/es2panda/util/ustring.h
@@ -200,6 +200,18 @@ public:
             return iter_ != sv_.end();
         }
 
+        bool HasExpectedNumberOfBytes(size_t count) const
+        {
+            for (size_t i = 0; i < count; ++i) {
+                if (!HasNext()) {
+                    return false;
+                }
+                iter_++;
+            }
+            iter_ -= count;
+            return true;
+        }
+
         void SkipCp() const;
 
     private:
@@ -235,6 +247,10 @@ private:
         static constexpr uint16_t UTF8_CONT_MASK = 0x3F;
         static constexpr uint16_t UTF8_CONT_HEADER = 0x80;
 
+        static constexpr size_t UTF8_NEXT_ONE_BYTE = 1;
+        static constexpr size_t UTF8_NEXT_TWO_BYTE = 2;
+        static constexpr size_t UTF8_NEXT_THREE_BYTE = 3;
+
         static constexpr char32_t SURROGATE_HIGH_MIN = 0xD800;
         static constexpr char32_t SURROGATE_HIGH_MAX = 0xDC00;
         static constexpr char32_t SURROGATE_LOW_MIN = 0xDC00;
@@ -322,15 +338,27 @@ char32_t StringView::Iterator::DecodeCP([[maybe_unused]] size_t *cpSize) const
     if (cu0 < Constants::UTF8_1BYTE_LIMIT) {
         res = cu0;
     } else if ((cu0 & Constants::UTF8_3BYTE_HEADER) == Constants::UTF8_2BYTE_HEADER) {
+        // Should be 2 bytes decoded in UTF-8, check if there is one byte following.
+        if (!HasExpectedNumberOfBytes(Constants::UTF8_NEXT_ONE_BYTE)) {
+            return INVALID_CP;
+        }
         char32_t cu1 = static_cast<uint8_t>(*iterNext++);
         res = ((cu0 & Constants::UTF8_2BYTE_MASK) << Constants::UTF8_2BYTE_SHIFT) | (cu1 & Constants::UTF8_CONT_MASK);
     } else if ((cu0 & Constants::UTF8_4BYTE_HEADER) == Constants::UTF8_3BYTE_HEADER) {
+        // Should be 3 bytes decoded in UTF-8, check if there are 2 bytes following.
+        if (!HasExpectedNumberOfBytes(Constants::UTF8_NEXT_TWO_BYTE)) {
+            return INVALID_CP;
+        }
         char32_t cu1 = static_cast<uint8_t>(*iterNext++);
         char32_t cu2 = static_cast<uint8_t>(*iterNext++);
         res = ((cu0 & Constants::UTF8_3BYTE_MASK) << Constants::UTF8_3BYTE_SHIFT) |
               ((cu1 & Constants::UTF8_CONT_MASK) << Constants::UTF8_2BYTE_SHIFT) | (cu2 & Constants::UTF8_CONT_MASK);
     } else if (((cu0 & Constants::UTF8_DECODE_4BYTE_MASK) == Constants::UTF8_4BYTE_HEADER) &&
                (cu0 <= Constants::UTF8_DECODE_4BYTE_LIMIT)) {
+        // Should be 4 bytes decoded in UTF-8, check if there are 3 bytes following.
+        if (!HasExpectedNumberOfBytes(Constants::UTF8_NEXT_THREE_BYTE)) {
+            return INVALID_CP;
+        }
         char32_t cu1 = static_cast<uint8_t>(*iterNext++);
         char32_t cu2 = static_cast<uint8_t>(*iterNext++);
         char32_t cu3 = static_cast<uint8_t>(*iterNext++);