fix: transaction.py: add extra check to script_GetOp

electrum/transaction.py

@@ -597,6 +597,7 @@ class BCDataStream(object):
 
 
 def script_GetOp(_bytes : bytes):
+    _bytes_len = len(_bytes)
     i = 0
     while i < len(_bytes):
         vch = None
@@ -617,6 +618,10 @@ def script_GetOp(_bytes : bytes):
                 try: (nSize,) = struct.unpack_from('<I', _bytes, i)
                 except struct.error: raise MalformedBitcoinScript()
                 i += 4
+
+            if nSize > _bytes_len - i:
+                raise MalformedBitcoinScript(f"Push of data element that is larger than remaining data: {nSize} vs {_bytes_len - i}")
+
             vch = _bytes[i:i + nSize]
             i += nSize