Microsoft Office products are a staple in most organizations and homes, making them a prime target for attackers. In 2022, a serious flaw labeled CVE-2022-29107 was discovered, allowing attackers to bypass critical security features in Microsoft Office. If you’re a sysadmin, cybersecurity enthusiast, or everyday Office user, understanding this vulnerability is essential to protect your data and your organization.

In this post, we’ll break down what CVE-2022-29107 is, how it works (with code snippets), potential exploit scenarios, patching advice, and reliable references.

What is CVE-2022-29107?

CVE-2022-29107 is a Security Feature Bypass vulnerability affecting various versions of Microsoft Office. A security feature bypass vulnerability allows an attacker to circumvent built-in safety controls. In this case, the vulnerability revolves around improper enforcement of Protected View — a sandbox intended to keep users safe when opening files from potentially unsafe sources like email or the internet.

Microsoft Security Update Guide:

CVE-2022-29107 - Security Update Guide

How Does the Vulnerability Work?

Microsoft Office enables Protected View when files are opened from untrusted locations (like email attachments or downloads from the web). CVE-2022-29107 occurs because Office improperly handles certain file types or locations, which can trick Office into opening dangerous files outside of Protected View. This gives potential malware the chance to run with fewer restrictions, making it easier to compromise your system.

The Exploit in Simple Terms

Attackers can create a specially crafted Office document (Word, Excel, etc.) hosted on a remote share or cloud location. When a victim opens the file, due to the bypass, Office fails to launch the file in Protected View. Instead, the file opens as if it were safe, and any embedded malicious code (like a macro or DDE attack) can execute.

Here’s what a basic exploitation might look like

1. Attacker prepares a malicious document and uploads it to a network share or OneDrive location that is white-listed (or misrecognized by Office).

Office opens the document in normal editing mode, not Protected View.

5. Malicious code executes, potentially installing malware, stealing credentials, or moving laterally through a network.

Example (Python) - Simulating a Malicious Document Drop

import os

# Attacker's UNC share location
unc_share = r'\\attacker-server\malicious-share'

# Simulate dropping a malicious Office file to a UNC location
malicious_file = unc_share + r'\invoice.docx'

# Send the link to the victim via email or chat
link = f'file://{malicious_file}'
print(f"Send this link to the victim: {link}")

> Once the victim clicks this link, their Office app may not properly activate Protected View due to the vulnerability, giving the attacker's code a chance to run.

A basic proof-of-concept macro could look like

Sub AutoOpen()
    ' This macro runs automatically when the document opens (not in Protected View)
    Shell "cmd.exe /c echo Hacked > %userprofile%\Desktop\hacked.txt", vbHide
End Sub

How Bad is the Risk?

- Attackers can trick users into opening files that *should* trigger a warning or be sandboxed, but instead run freely.
- Social engineering: Combined with phishing, CVE-2022-29107 can make users believe a document is from a trusted source.
- Potential for malware/ransomware deployment: Lack of sandboxing gives malware free rein if macro execution is also enabled.

Microsoft Office 2013, 2016, 2019, and Microsoft 365 Apps prior to June 2022 updates.

- Systems that access files from network shares, cloud storage, or via external links (very common scenarios).
- Users/organizations relying heavily on Protected View as a line of defense.

Install the official Microsoft security update for your version:

Microsoft Security Update Guide

Microsoft CVE-2022-29107 Advisory:

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-29107

NVD (National Vulnerability Database):

https://nvd.nist.gov/vuln/detail/CVE-2022-29107

Red Team Guide to Office Document Attacks (background):

https://redcanary.com/blog/office-macros

Mitre CWE-693 — Protection Mechanism Failure:

https://cwe.mitre.org/data/definitions/693.html

Conclusion

CVE-2022-29107 is an important reminder: security features aren’t fool-proof if they’re not properly enforced. Attackers are always looking for shortcuts, and in 2022, they found one in Microsoft Office’s handling of Protected View.

Patch your devices, educate your team, and keep an eye on future updates. Only by staying proactive can you keep safe from the constant threat of document-based attacks.

Timeline

Published on: 05/10/2022 21:15:00 UTC
Last modified on: 05/19/2022 20:49:00 UTC