CVE-2024-21409: Microsoft .NET Framework RCE Vulnerability

CVE-2024-21409 Overview

CVE-2024-21409 is a Use After Free (CWE-416) remote code execution vulnerability affecting Microsoft .NET, .NET Framework, Visual Studio, and PowerShell. This vulnerability allows an attacker with local access to execute arbitrary code on affected systems when a user interacts with a specially crafted file or application. The vulnerability exists due to improper memory management in the .NET runtime, where objects may be accessed after they have been freed from memory.

Critical Impact

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code with the privileges of the current user, potentially leading to complete system compromise. The vulnerability affects a wide range of Microsoft products across multiple Windows versions.

Affected Products

• Microsoft .NET Framework 3.5, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, and 4.8.1
• Microsoft .NET (multiple versions)
• Microsoft Visual Studio 2022 (multiple editions)
• Microsoft PowerShell (multiple versions)
• Microsoft Windows 10 (versions 1607, 1809, 21H2, 22H2)
• Microsoft Windows 11 (versions 21H2, 22H2, 23H2)
• Microsoft Windows Server 2008 SP2/R2 SP1, 2012, 2012 R2, 2016, 2019, 2022

Discovery Timeline

• April 9, 2024 - CVE-2024-21409 published to NVD
• January 17, 2025 - Last updated in NVD database

Technical Details for CVE-2024-21409

Vulnerability Analysis

This vulnerability is classified as a Use After Free (UAF) memory corruption issue in the .NET runtime environment. Use After Free vulnerabilities occur when a program continues to reference memory after it has been deallocated, allowing an attacker to manipulate the freed memory region to achieve code execution.

The attack requires local access to the target system and user interaction, meaning an attacker would need to convince a user to open a malicious file or application that triggers the vulnerable code path. Once triggered, the vulnerability can lead to arbitrary code execution in the context of the current user, potentially resulting in full system compromise if the user has elevated privileges.

The broad attack surface encompasses .NET Framework, .NET Core, Visual Studio, and PowerShell, making this vulnerability particularly impactful for enterprise environments where these components are widely deployed for development and automation tasks.

Root Cause

The root cause of CVE-2024-21409 lies in improper memory lifecycle management within the .NET runtime. Specifically, memory that has been freed continues to be referenced by the application, creating a dangling pointer situation. When an attacker can control the contents of the freed memory region before it is accessed again, they can redirect program execution to attacker-controlled code.

This type of vulnerability often occurs in complex runtime environments like .NET where garbage collection and manual memory management must work together, and edge cases in object lifetime management can lead to premature deallocation.

Attack Vector

The attack vector for CVE-2024-21409 requires local access and user interaction. An attacker would typically craft a malicious file or application that exploits the Use After Free condition when processed by one of the affected Microsoft components.

The exploitation scenario involves manipulating heap memory layout to place attacker-controlled data in the freed memory region. When the vulnerable code attempts to use the stale pointer, it accesses the attacker's payload instead, enabling arbitrary code execution.

Given the local attack vector and user interaction requirement, common attack scenarios include distributing malicious files via email attachments, compromised downloads, or social engineering tactics to convince users to run malicious .NET applications or scripts.

Detection Methods for CVE-2024-21409

Indicators of Compromise

• Unexpected crashes or exceptions in .NET applications, Visual Studio, or PowerShell processes
• Memory access violations or heap corruption events in Windows Event Logs related to clr.dll or .NET runtime components
• Suspicious .NET assemblies or PowerShell scripts with obfuscated code attempting memory manipulation

Detection Strategies

• Monitor for unusual process behavior patterns in devenv.exe, pwsh.exe, powershell.exe, and .NET application processes
• Implement application whitelisting to prevent execution of unauthorized .NET assemblies and PowerShell scripts
• Deploy endpoint detection and response (EDR) solutions capable of detecting memory corruption exploitation techniques

Monitoring Recommendations

• Enable Windows Defender Application Control (WDAC) or AppLocker policies to restrict .NET assembly execution
• Configure enhanced logging for PowerShell script block logging and module logging via Group Policy
• Monitor for suspicious memory allocation patterns and heap spray attempts using SentinelOne's behavioral AI detection capabilities

How to Mitigate CVE-2024-21409

Immediate Actions Required

• Apply Microsoft security updates from the April 2024 Patch Tuesday release immediately
• Prioritize patching development workstations and servers running Visual Studio, .NET applications, and PowerShell
• Restrict user permissions to minimize the impact of potential exploitation
• Educate users about the risks of opening untrusted files or running unknown applications

Patch Information

Microsoft has released security updates addressing CVE-2024-21409 as part of their April 2024 security update cycle. Administrators should apply the appropriate updates for all affected components including .NET Framework, .NET, Visual Studio 2022, and PowerShell.

For detailed patch information and download links, refer to the Microsoft Security Update Guide for CVE-2024-21409. Organizations using NetApp products should also review the NetApp Advisory NTAP-20250117-0002 for additional guidance.

Workarounds

• Implement strict application control policies to limit execution of untrusted .NET assemblies and scripts
• Configure PowerShell execution policies to restrict script execution in environments where administrative access is limited
• Deploy network segmentation to isolate development environments from critical production systems
• Enable Controlled Folder Access in Windows Security to protect sensitive directories from unauthorized modifications

# PowerShell execution policy configuration example
Set-ExecutionPolicy -ExecutionPolicy AllSigned -Scope LocalMachine
# Enable script block logging via Group Policy or registry
Set-ItemProperty -Path "HKLM:\SOFTWARE\Wow6432Node\Policies\Microsoft\Windows\PowerShell\ScriptBlockLogging" -Name "EnableScriptBlockLogging" -Value 1