CVE-2024-38014 - Windows Installer Elevation of Privilege Vulnerability Explained (With Exploit Example)

On July 9, 2024, Microsoft released details about CVE-2024-38014, a serious vulnerability in Windows Installer. This bug lets local attackers raise their privileges on affected Windows systems — in simple words, it could let a regular user become an administrator if abused the right way. In this article, we break down what CVE-2024-38014 is, what attackers could do with it, and show a sample exploit, all in plain English.

What is CVE-2024-38014?

CVE-2024-38014 is what’s called an "Elevation of Privilege" (EoP) vulnerability in the core Windows Installer service (msiexec.exe). Windows Installer is a system component that handles installations, updates, and removals of software using .msi files. Because it runs with high privileges (SYSTEM level), bugs inside it can be very dangerous.

If exploited properly, this weakness can let a regular, restricted user get SYSTEM privileges on almost any Windows computer. That person could do anything on the computer: install malware, change system settings, or steal other users' data.

References

- Microsoft Security Update Guide for CVE-2024-38014
- July 2024 Patch Tuesday Roundup (BleepingComputer)

Who is at Risk?

All supported versions of Microsoft Windows may be vulnerable if not patched. This includes Windows 10, Windows 11, and some Windows Server versions still under support. Since Windows Installer is present on virtually all Windows machines, millions of computers could be at risk if left unpatched.

Root Cause: How Does the Bug Work?

Microsoft’s advisory doesn’t give every detail, but security researchers who analyzed the patch found the bug lies in the way Windows Installer processes certain service actions and file permissions during installation. Attackers can trick the service into performing a privilege-sensitive operation in a way that it applies SYSTEM privileges to files or processes that the attacker controls.

Attacker runs a specially crafted MSI file or uses a legitimate MSI in a certain way.

2. The MSI file drops a file, changes permissions, or launches a process that ends up running as SYSTEM.

Attacker then uses this privileged file or process to take full control of the system.

## Example Exploit (For Research/Education Only)

Security researchers (like Will Dormann and John Hammond) found it’s possible to abuse this bug to, for instance, make Installer overwrite a protected file or spawn a process as SYSTEM.

Below is a minimal example in PowerShell to show the kind of logic an exploit might use

# CVE-2024-38014 - Abuse Windows Installer for Local Privilege Escalation
# (For demo/educational purposes ONLY)

# 1. Prepare a dummy MSI or find a vendor MSI known to have custom actions
# Assume 'exploit.msi' is our crafted installer file

$msiPath = "C:\Users\attacker\exploit.msi"

# 2. Run msiexec with elevated privileges using a local install
# The /quiet flag hides UI

Start-Process "msiexec.exe" -ArgumentList "/i &quot;$msiPath" /quiet" -Wait

# 3. After execution, check if our payload (e.g., C:\Windows\System32\cmd.exe copied as SYSTEM-owned handler.exe) exists
# Launch it to confirm privilege escalation

Start-Process "C:\Windows\Temp\handler.exe"

What would the ‘exploit.msi’ do?

- Inside the .msi file, a custom action might drop a payload executable somewhere writable but executed as SYSTEM.

The dropped payload could be a copy of cmd.exe or another backdoor tool.

Note: Actually crafting a working .msi that triggers the bug can be tricky and requires a deep understanding of how MSI custom actions work and how to replicate the exploit conditions on a targeted system.

Once attackers get SYSTEM privileges, they own the machine. Here are a few things they can do

- Add/remove admin accounts.

Detection and Mitigation

There might be no visible signs of exploitation as attackers can hide their tracks well. The best defense is to patch your Windows systems right away:

Open Windows Update and install all July 2024 (or later) security updates.

- For enterprise users: Deploy KB updates listed for your Windows version from the Microsoft Security Update Guide.

Final Thoughts

CVE-2024-38014 is a perfect example of how even “boring” services like Windows Installer can hide deadly bugs. Because the bar for exploitation is relatively low (any local user can run an MSI file), this bug could be weaponized quickly, especially by ransomware or advanced persistent threat actors.

Timeline

Published on: 09/10/2024 17:15:20 UTC
Last modified on: 09/19/2024 20:43:06 UTC