CVE-2024-20657 - Breaking Down the Windows Group Policy Elevation of Privilege Vulnerability
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In early 2024, Microsoft patched a serious vulnerability tagged as CVE-2024-20657 that affects the Windows Group Policy service. This bug allows attackers to get higher privileges on a system—a problem that could let bad actors gain the keys to the kingdom in many organizations. Here, we’ll unpack what this means, offer real-world context, show example code, link to trusted resources, and break down a potential exploit path.
What Is CVE-2024-20657?
This vulnerability is found in the Microsoft Windows Group Policy component. Group Policy is what administrators use to manage configurations across lots of Windows computers in a domain. The bug lets a regular user (not an admin!) escalate their permissions and potentially run code as SYSTEM—the most powerful account on a Windows computer.
Microsoft says:
*“A locally authenticated attacker could exploit this vulnerability to gain elevated privileges.”*
Affected Platforms: Windows 10, 11, Windows Server 2016-2022
- Severity: High (CVSS: 7.8 source)
How Does The Vulnerability Work?
Group Policy tasks sometimes involve copying files, creating scheduled tasks, or updating system configurations. If these processes aren’t locked down correctly, a normal user might be able to trick the system into running their own stuff with SYSTEM privileges. Bugs like this often pop up due to improper permissions or path handling—letting a user control a file, folder, or resource that SYSTEM later trusts.
The basic idea:
1. Identifying a Writable Path
Suppose the Group Policy Client creates a folder during updates at C:\Windows\Temp\gpupdate and sets weak folder permissions.
# Check permissions on the folder
icacls C:\Windows\Temp\gpupdate
If the output shows "BUILTIN\Users:(OI)(CI)(W)..." then regular users can write here.
2. Planting a Malicious Executable
If you can drop a file in a folder that SYSTEM will later execute, you can escalate.
# Plant a backdoor executable
Copy-Item .\evil.exe C:\Windows\Temp\gpupdate\gptemp.exe
3. Triggering Execution
Depending on the bug details (kept vague until full disclosure and patching), Group Policy may run anything named like gptemp.exe inside that folder.
# Force a Group Policy update, which may trigger SYSTEM to run our code
gpupdate /force
Now your evil.exe runs as SYSTEM, giving you privileges to do almost anything.
Live Proof of Concept? Example Shell
Warning: Don’t do this on production or unauthorized systems!
# Malicious payload to create a SYSTEM-level admin user
echo net user attacker Passwrd! /add > C:\Windows\Temp\gpupdate\gptemp.bat
echo net localgroup administrators attacker /add >> C:\Windows\Temp\gpupdate\gptemp.bat
If the vulnerability is unpatched and Group Policy blindly executes this, your attacker user gets created with SYSTEM rights.
How to Defend Against CVE-2024-20657
Patch, patch, patch!
Microsoft released the fix in the January 2024 Patch Tuesday update:
- Microsoft Security Advisory
- Original Patch Details
Extra Steps:
More Resources
- Microsoft Security Response Center Advisory
- NIST NVD Entry
- Red Team Notes: Living Off the Land with GP
Final Words
CVE-2024-20657 stands as a reminder that privilege escalation bugs in core Windows services like Group Policy can be absolutely devastating. Anyone managing Windows computers in a network must prioritize patching these flaws. If you’re a defender, focus on patch cycles and permissions audits. If you’re an attacker—well, now you know you’re running out of time!
Stay sharp, keep those endpoints up to date, and always follow security best practices!
Disclaimer:
This information is for educational purposes only. Do not attempt these techniques on any system you do not own or have explicit permission to test.
Timeline
Published on: 01/09/2024 18:15:48 UTC
Last modified on: 04/11/2024 20:15:11 UTC