CVE-2022-30173 - Microsoft Excel Remote Code Execution Vulnerability

Microsoft Excel is a staple in millions of businesses and homes. But in 2022, a dangerous security hole—CVE-2022-30173—was discovered in this widely used program. This post dives deep into what CVE-2022-30173 is, why it matters, how it can be exploited (with code snippets), and where to find more details straight from trusted sources.

What is CVE-2022-30173?

CVE-2022-30173 is a high-severity remote code execution (RCE) vulnerability in Microsoft Excel. Simply put, it lets attackers run any code they choose on your computer *just by opening a crafted Excel file*. If you think reading emails and opening spreadsheets is safe, think again!

Older versions (if not patched)

*For a full list, see the Microsoft Security Update Guide.*

How Does The Exploit Work?

The flaw lurks in Excel’s method of parsing certain objects within a spreadsheet. Hackers can craft a corrupt Excel file that includes either an embedded malicious object (like a macro or OLE object), or abuses a buffer overflow to run code of their choice.

Here’s a simple breakdown

1. Malicious Excel file is crafted. This file holds payload code—often as a macro, but this CVE can also work without macros.
2. Victim opens the file. Excel processes the file and triggers the vulnerability, running the payload.

Exploit Example: Creating a Malicious Excel File

WARNING: For educational purposes only. Never run untrusted code on your machine.

Below is a Python snippet using the oletools and openpyxl libraries to create a basic malicious Excel document that could exploit this or similar vulnerabilities by embedding an OLE object. For this CVE, real-world exploits often used more complex payloads, but the sample illustrates the process:

import oletools.olevba
from openpyxl import Workbook

# Step 1: Create a new Excel file
wb = Workbook()
ws = wb.active
ws['A1'] = 'Hello, open this file :)'

# Step 2: Save and close the workbook
wb.save("malicious.xlsx")

# Step 3: Embed malicious macro (VBA code)
vba_code = '''
Sub AutoOpen()
    Shell "calc.exe", vbNormalFocus
End Sub
'''

# Use oletools or add VBA project with Excel manually
# For demonstration, we just explain the VBA part:
print("Add this VBA macro to run calc.exe when opened:")
print(vba_code)

In practice, attackers combine tools to inject the exploit in the Excel file itself. Tools such as oletools, EvilClippy, and even hex editors are often used.

Exploit Chain Simplified

1. Phishing email sent with .xls/.xlsx attachment.

Check these links for in-depth analysis and PoC videos

- CVE-2022-30173 at Microsoft
- MITRE CVE Record

Example exploit writeup:

Exploit-DB Reference

Patch and Fix

Microsoft patched this vulnerability in June 2022. See their official bulletin for updates and technical details.

Conclusion

CVE-2022-30173 is a prime example of just how dangerous seemingly simple files can be. Attackers don’t need complex tricks—just an Excel file and a willing user. Make sure your systems are patched, train users, and stay skeptical of unexpected attachments. For organizations, regular vulnerability scanning and aggressive patch management are key.

Be safe out there—and think before you click!

> References
> - Microsoft Security Update Guide - CVE-2022-30173
> - MITRE CVE Record
> - Exploit-DB Reference
> - oletools Documentation
> - EvilClippy for MS Office Document Weaponization

If you found this post useful, share it to raise awareness—every user protected could be a disaster avoided.

Timeline

Published on: 06/15/2022 22:15:00 UTC
Last modified on: 06/25/2022 03:39:00 UTC