CVE-2021-40444 PoC — Microsoft MSHTML Remote Code Execution Vulnerability

Title:Microsoft MSHTML Remote Code Execution Vulnerability (CVE-2021-40444)
Description:<p>Microsoft is investigating reports of a remote code execution vulnerability in MSHTML that affects Microsoft Windows. Microsoft is aware of targeted attacks that attempt to exploit this vulnerability by using specially-crafted Microsoft Office documents.</p> <p>An attacker could craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser rendering engine. The attacker would then have to convince the user to open the malicious document. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.</p> <p>Microsoft Defender Antivirus and Microsoft Defender for Endpoint both provide detection and protections for the known vulnerability. Customers should keep antimalware products up to date. Customers who utilize automatic updates do not need to take additional action. Enterprise customers who manage updates should select the detection build 1.349.22.0 or newer and deploy it across their environments. Microsoft Defender for Endpoint alerts will be displayed as: “Suspicious Cpl File Execution”.</p> <p>Upon completion of this investigation, Microsoft will take the appropriate action to help protect our customers. This may include providing a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs.</p> <p>Please see the <strong>Mitigations</strong> and <strong>Workaround</strong> sections for important information about steps you can take to protect your system from this vulnerability.</p> <p><strong>UPDATE</strong> September 14, 2021: Microsoft has released security updates to address this vulnerability. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. Please see the FAQ for important information about which updates are applicable to your system.</p>

Reverse engineering the "A Letter Before Court 4.docx" malicious files exploting cve-2021-40444

# cve-2021-40444
Reverse engineering the "A Letter Before Court 4.docx" malicious files exploting cve-2021-40444

Files (including malicious word and cab-file) may be downloaded on any.run: https://app.any.run/tasks/36c14029-9df8-439c-bba0-45f2643b0c70/#

**Note!**
The domain name in the original malicious code is **replaced with 127.0.0.1:8000** to avoid any mistakes executing malicious code.
So, if you want to serve your own championship.inf-file (which is actually a PE-file), just use:

python3 -m http.server

**The step 3 file**
In this step, the code is human readably enough to see how the cve-2021-40444 bug is used by the malicious word document.

**championship.inf**
This is the PE-file that is loaded on a successful attack.

**Stages**
1. Word file loads the web-address (internet address) as an OLE-object (side.html in this case)
2. Side.html uses ActiveX loading to download a .cab file from internet 
3. Side.html javascript references the championship.inf contained in the .cab file as a loadable activex-object
4. Thereafter... code execution by the activex

 [4.0K]  /data/pocs/da863c808521de56bf4a1459e3622e8966c21cb5
├── [1.1K]  README.md
├── [7.7K]  side_step1.html
├── [6.2K]  side_step2.html
└── [3.4K]  side_step3.html

0 directories, 4 files