Fix buffer overflow in string radix conversion

jerry-core/ecma/base/ecma-helpers-conversion.c

@@ -368,16 +368,6 @@ ecma_utf8_string_to_number (const lit_utf8_byte_t *str_p, /**< utf-8 string */
 
   bool sign = false;
 
-  if (*str_p == LIT_CHAR_PLUS)
-  {
-    str_p++;
-  }
-  else if (*str_p == LIT_CHAR_MINUS)
-  {
-    sign = true;
-    str_p++;
-  }
-
   if (str_p + 2 < end_p && str_p[0] == LIT_CHAR_0)
   {
     uint8_t radix = lit_char_to_radix (str_p[1]);
@@ -388,6 +378,16 @@ ecma_utf8_string_to_number (const lit_utf8_byte_t *str_p, /**< utf-8 string */
     }
   }
 
+  if (*str_p == LIT_CHAR_PLUS)
+  {
+    str_p++;
+  }
+  else if (*str_p == LIT_CHAR_MINUS)
+  {
+    sign = true;
+    str_p++;
+  }
+
   /* Check if string is equal to "Infinity". */
   const lit_utf8_byte_t *infinity_str_p = lit_get_magic_string_utf8 (LIT_MAGIC_STRING_INFINITY_UL);
   const lit_utf8_size_t infinity_length = lit_get_magic_string_size (LIT_MAGIC_STRING_INFINITY_UL);

jerry-core/ecma/base/ecma-helpers-number.c

@@ -659,7 +659,7 @@ ecma_number_parse_float (const lit_utf8_byte_t *str_p, /**< routine's first argu
   }
 
   /* 5. */
-  ecma_number_t ret_num = ecma_utf8_string_to_number (num_start_p, (lit_utf8_size_t) (num_end_p - num_start_p), 0);
+  ecma_number_t ret_num = ecma_utf8_string_to_number (num_start_p, num_size, 0);
 
   if (sign)
   {

tests/jerry/regression-test-issue-4850.js

@@ -0,0 +1,23 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// 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.
+
+assert(Number('0x10') === 16);
+assert(isNaN(Number('+0x10')));
+assert(isNaN(Number('-0x10')));
+assert(parseFloat('0x10') === 0);
+assert(parseFloat('+0x10') === 0);
+assert(parseFloat('-0x10') === 0);
+assert(0x10 === 16);
+assert(+0x10 === 16);
+assert(-0x10 === -16);