static CURLcode smtp_perform_authentication(struct connectdata *conn)
{
  CURLcode result = CURLE_OK;
  struct smtp_conn *smtpc = &conn->proto.smtpc;
  saslprogress progress;

  /* Check we have enough data to authenticate with, and the
     server supports authentiation, and end the connect phase if not */
  if(!smtpc->auth_supported ||
     !Curl_sasl_can_authenticate(&smtpc->sasl, conn)) {
    state(conn, SMTP_STOP);
    return result;
  }

  /* Calculate the SASL login details */
  result = Curl_sasl_start(&smtpc->sasl, conn, FALSE, &progress);

  if(!result) {
    if(progress == SASL_INPROGRESS)
      state(conn, SMTP_AUTH);
    else {
      /* Other mechanisms not supported */
      infof(conn->data, "No known authentication mechanisms supported!\n");
      result = CURLE_LOGIN_DENIED;
    }
  }

  return result;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.