Transaction Malformed - Stellar Developer Docs

The transaction_malformed error returns a 400 error code and occurs when a client submits a malformed transaction. There are many ways in which a transaction could be malformed, including:

You submitted an empty string.
Your base64-encoded string is invalid.
Your XDR structure is invalid.
You have leftover bytes in your XDR structure.

Example Response for a Status Code

{
  "type": "https://stellar.org/horizon-errors/transaction_malformed",
  "title": "Transaction Malformed",
  "status": 400,
  "detail": "Horizon could not decode the transaction envelope in this request. A transaction should be an XDR TransactionEnvelope struct encoded using base64.  The envelope read from this request is echoed in the `extras.envelope_xdr` field of this response for your convenience.",
  "extras": {
    "envelope_xdr": "BBBBBPORy3CoX6ox2ilbeiVjBA5WlpCSZRcjZ7VE9Wf4QVk7AAAAZAAAQz0AAAACAAAAAAAAAAAAAAABAAAAAAAAAAEAAAAA85HLcKhfqjHaKVt6JWMEDlaWkJJlFyNntUT1Z/hBWTsAAAAAAAAAAAL68IAAAAAAAAAAARN17BEAAABAA9Ad7OKc7y60NT/JuobaHOfmuq8KbZqcV6G/es94u9yT84fi0aI7tJsFMOyy8cZ4meY3Nn908OU+KfRWV40UCw=="
  }
}