CVE-2026-20925
📋 TL;DR
This vulnerability allows an attacker to manipulate file paths in Windows NTLM authentication, enabling network spoofing attacks. Attackers can potentially impersonate legitimate users or services by controlling file names or paths. Systems using Windows NTLM authentication are affected.
💻 Affected Systems
- Windows NTLM implementation
📦 What is this software?
Windows 10 1607 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
Windows 11 25h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete network compromise through credential theft, lateral movement across the network, and domain controller impersonation.
Likely Case
Unauthorized access to network resources, data exfiltration, and privilege escalation within the network.
If Mitigated
Limited to isolated network segments with proper segmentation and monitoring in place.
🎯 Exploit Status
Requires network access and ability to manipulate NTLM authentication flows.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update for specific KB number
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20925
Restart Required: Yes
Instructions:
1. Apply latest Windows security updates from Microsoft. 2. Restart affected systems. 3. Verify patch installation via Windows Update history.
🔧 Temporary Workarounds
Disable NTLM authentication
windowsReplace NTLM with Kerberos authentication where possible
Group Policy: Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options > Network security: Restrict NTLM
Implement network segmentation
allIsolate systems using NTLM to limit attack surface
🧯 If You Can't Patch
- Implement strict network monitoring for NTLM authentication anomalies
- Enforce multi-factor authentication for all privileged accounts
🔍 How to Verify
Check if Vulnerable:
Check Windows version and patch level against Microsoft advisoryCheck Version:
wmic os get caption,version,buildnumberVerify Fix Applied:
Verify Windows Update history contains the relevant security update KB📡 Detection & Monitoring
Log Indicators:
- Unusual NTLM authentication patterns
- Failed authentication attempts from unexpected sources
- File path manipulation in authentication logs
Network Indicators:
- Abnormal NTLM traffic patterns
- Suspicious SMB or LDAP authentication requests
SIEM Query:
source="windows-security" EventID=4625 OR EventID=4648 | where authentication_package="NTLM" | stats count by src_ip