CVE-2025-30399
📋 TL;DR
This CVE describes an untrusted search path vulnerability in .NET and Visual Studio that allows attackers to execute arbitrary code by manipulating the search order for DLLs or other files. Attackers can exploit this over a network to compromise systems running vulnerable versions. Organizations using affected .NET or Visual Studio installations are at risk.
💻 Affected Systems
- .NET Framework
- Visual Studio
📦 What is this software?
.net by Microsoft
.net by Microsoft
Powershell by Microsoft
Powershell by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with remote code execution leading to data theft, ransomware deployment, or complete system takeover.
Likely Case
Attacker gains initial foothold on target system, potentially leading to lateral movement within the network and privilege escalation.
If Mitigated
Attack fails due to proper access controls, network segmentation, or exploitation attempts being blocked by security controls.
🎯 Exploit Status
Exploitation requires network access and ability to place malicious files in search path; no public exploit code known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: To be determined from Microsoft Security Update
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-30399
Restart Required: Yes
Instructions:
1. Visit Microsoft Security Update Guide for CVE-2025-30399
2. Download appropriate security update for your .NET/Visual Studio version
3. Install update following Microsoft's instructions
4. Restart affected systems as required
🔧 Temporary Workarounds
Restrict network access
allLimit network access to systems running vulnerable .NET/Visual Studio installations
Use firewall rules to restrict inbound connections to affected systems
Implement application whitelisting
windowsPrevent execution of unauthorized DLLs and executables
Configure Windows AppLocker or similar application control solutions
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems
- Deploy endpoint detection and response (EDR) solutions to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check installed .NET/Visual Studio versions against Microsoft's security advisoryCheck Version:
For .NET: reg query "HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP" /sVerify Fix Applied:
Verify security update is installed via Windows Update history or version check📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from .NET/Visual Studio executables
- Failed DLL loading attempts from unexpected locations
- Network connections to suspicious locations from .NET processes
Network Indicators:
- Unexpected network traffic to/from systems running .NET/Visual Studio
- SMB or other file sharing protocol anomalies
SIEM Query:
Process creation where parent process contains 'dotnet' OR 'devenv' AND command line contains unusual paths