CVE-2021-40444 builders

This repo contain builders of cab file, html file, and docx file for CVE-2021-40444 exploit. This repo is just for testing, research and educational purposes. You are responsible for how you use the code provided in this repo.

The code is developed by reversing malware samples found in wild and shared by various security researchers.

The builders for this CVE are already public. The purpose of this repo is to check how effectively we can bypass static detections by different AV vendors for the docx files, at the time of writing.

The JS code can easily obfuscated by online tools or manually. But the docx file contains just one file which is document.xml.rels, on which the signatures can be based. What we can tamper in it so we can evade static detections of most of the AV.

The cabrc.exe is Microsoft exe included in Internet Explorer Administration Kit and can be downloaded from and after installation you would find this exe in “C:\Program Files (x86)\Windows IEAK 11”

There are 3 builders.

The code works for python 2.7

First go to CVE-2021-40444 folder and place your dll file there and rename it to IEcache.inf (or you can use the calc dll already there).

Then go to source folder and generate the cab file


Upload your cab file, and using the cab file URL generate the html file

c:\cve-2021-40444\sources\python tests.txt (Note instead of using html extension, if we use .txt the exploit still works, but bypasses AV)

Now finally upload your html file and generate the doc file. Use HTTP (capital) instead of http, and “” instead of “/”, to bypass AV. And we dont need x-usc: too.

example: c:\cve-2021-40444\sources\python\ HTTP:\\\new\tests.txt

The result is in front of you.
[email protected]