CVE-2025-21171: Microsoft .NET RCE Vulnerability

CVE-2025-21171 Overview

CVE-2025-21171 is a remote code execution vulnerability affecting Microsoft .NET and related development tools. This heap-based buffer overflow vulnerability (CWE-122) allows attackers to execute arbitrary code on vulnerable systems through network-based attacks. The vulnerability impacts multiple Microsoft products including .NET 9.0.0, PowerShell 7.5, and Visual Studio 2022, and affects systems running Windows, macOS, and Linux.

Critical Impact

Successful exploitation of this vulnerability could allow an attacker to achieve remote code execution with the privileges of the current user, potentially leading to complete system compromise across multiple operating system platforms.

Affected Products

• Microsoft .NET 9.0.0
• Microsoft PowerShell 7.5
• Microsoft Visual Studio 2022
• Windows, macOS, and Linux operating systems running affected .NET components

Discovery Timeline

• January 14, 2025 - CVE-2025-21171 published to NVD
• July 10, 2025 - Last updated in NVD database

Technical Details for CVE-2025-21171

Vulnerability Analysis

This vulnerability stems from a heap-based buffer overflow condition (CWE-122) within the .NET framework. Heap-based buffer overflows occur when a program writes data beyond the allocated memory buffer on the heap, potentially corrupting adjacent memory structures. In the context of .NET applications, this type of memory corruption can lead to arbitrary code execution.

The attack requires network access and user interaction, indicating that exploitation likely involves crafted input or malicious content that must be processed by a .NET application. The cross-platform nature of .NET means this vulnerability affects applications running on Windows, macOS, and Linux environments.

Root Cause

The root cause is a heap-based buffer overflow (CWE-122) in the .NET runtime. This class of vulnerability occurs when memory operations fail to properly validate buffer boundaries, allowing an attacker to write beyond allocated heap memory regions. This can corrupt heap metadata or adjacent objects, enabling control flow hijacking and ultimately code execution.

Attack Vector

The attack vector is network-based, requiring user interaction for successful exploitation. An attacker could exploit this vulnerability by:

1. Crafting malicious input that triggers the buffer overflow condition when processed by a vulnerable .NET application
2. Delivering the malicious content to a victim through network channels (such as web content, files, or network protocols)
3. Requiring the victim to interact with or process the malicious content

The vulnerability allows an unauthenticated attacker to achieve high impact on confidentiality, integrity, and availability of the target system. The complexity of exploitation is considered high, indicating that reliable exploitation may require specific conditions or additional steps.

Detection Methods for CVE-2025-21171

Indicators of Compromise

• Unexpected crashes or exceptions in .NET applications, particularly those processing external input
• Memory corruption artifacts or abnormal heap behavior in .NET runtime processes
• Suspicious network activity targeting .NET-based applications or services
• Evidence of code execution following .NET application anomalies

Detection Strategies

• Monitor .NET application event logs for unhandled exceptions or access violations related to memory operations
• Deploy endpoint detection and response (EDR) solutions to detect suspicious process behavior following .NET runtime activity
• Implement network traffic analysis to identify potentially malicious payloads targeting .NET applications
• Use application-level logging to track input processing anomalies

Monitoring Recommendations

• Enable Windows Event Logging for .NET Runtime events, including Application Error events (Event ID 1000) and .NET Runtime errors
• Monitor for suspicious child process creation from .NET applications that could indicate successful code execution
• Implement file integrity monitoring for .NET binaries and configuration files
• Track Visual Studio and PowerShell process behavior for anomalous activity

How to Mitigate CVE-2025-21171

Immediate Actions Required

• Apply the latest security updates from Microsoft for .NET, PowerShell, and Visual Studio 2022
• Review and update all deployed applications using affected .NET versions
• Restrict network exposure of vulnerable .NET applications until patching is complete
• Implement defense-in-depth measures including network segmentation and application-level controls

Patch Information

Microsoft has released security updates to address this vulnerability. Administrators should consult the Microsoft Security Response Center advisory for detailed patch information and update guidance. Organizations should prioritize updating:

• .NET SDK and Runtime to patched versions
• PowerShell 7.5 to the latest security release
• Visual Studio 2022 through the Visual Studio Installer

Workarounds

• Limit network exposure of .NET applications to trusted networks until patches can be applied
• Implement strict input validation at application boundaries to reduce attack surface
• Consider application sandboxing or containerization to limit the impact of potential exploitation
• Enable Address Space Layout Randomization (ASLR) and other exploit mitigation technologies where available

# Verify installed .NET SDK versions
dotnet --list-sdks

# Verify installed .NET runtime versions
dotnet --list-runtimes

# Update .NET SDK to latest patched version
dotnet new update