diff --git a/core/src/main/java/com/alibaba/fastjson2/JSONReaderASCII.java b/core/src/main/java/com/alibaba/fastjson2/JSONReaderASCII.java
index f1b8a2c43f..8a09eb0ab7 100644
--- a/core/src/main/java/com/alibaba/fastjson2/JSONReaderASCII.java
+++ b/core/src/main/java/com/alibaba/fastjson2/JSONReaderASCII.java
@@ -946,6 +946,9 @@ public final String readFieldName() {
             int c = bytes[offset];
             if (c == '\\') {
                 nameEscape = true;
+                if (offset + 1 >= end) {
+                    throw new JSONException(info("illegal input"));
+                }
                 c = bytes[offset + 1];
                 offset += (c == 'u' ? 6 : (c == 'x' ? 4 : 2));
                 continue;