CVE-2022-26937
📋 TL;DR
CVE-2022-26937 is a critical remote code execution vulnerability in Windows Network File System (NFS) that allows unauthenticated attackers to execute arbitrary code on vulnerable systems. This affects Windows servers running NFS services, potentially allowing complete system compromise. Organizations using Windows Server with NFS enabled are at risk.
💻 Affected Systems
- Windows Server
📦 What is this software?
Windows Server by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover with SYSTEM privileges, enabling data theft, ransomware deployment, lateral movement, and persistent backdoor installation.
Likely Case
Remote code execution leading to credential harvesting, data exfiltration, and deployment of malware or ransomware on affected servers.
If Mitigated
Limited impact if NFS services are disabled or network segmentation prevents access; patched systems remain unaffected.
🎯 Exploit Status
Public proof-of-concept code exists, and the high CVSS score with unauthenticated remote execution makes weaponization highly probable.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: May 2022 security updates (KB5013952 for Server 2022, KB5013951 for Server 2019, etc.)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2022-26937
Restart Required: Yes
Instructions:
1. Apply May 2022 Windows Server security updates via Windows Update. 2. Alternatively, download and install the specific KB patch for your Windows Server version. 3. Restart the server after installation.
🔧 Temporary Workarounds
Disable NFS Service
windowsTemporarily disable the Network File System service if not required
Stop-Service -Name NfsServer
Set-Service -Name NfsServer -StartupType Disabled
Block NFS Ports
windowsBlock network access to NFS ports (2049 TCP/UDP) at firewall
New-NetFirewallRule -DisplayName "Block NFS" -Direction Inbound -Protocol TCP -LocalPort 2049 -Action Block
New-NetFirewallRule -DisplayName "Block NFS UDP" -Direction Inbound -Protocol UDP -LocalPort 2049 -Action Block
🧯 If You Can't Patch
- Disable NFS services immediately on all affected servers
- Implement strict network segmentation to isolate NFS servers from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Check if NFS Server service is running: Get-Service NfsServer | Select Status, and verify Windows Server version is unpatched for May 2022.Check Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify May 2022 security updates are installed: Get-HotFix -Id KB5013952, KB5013951, or relevant KB for your version, and confirm NfsServer service status.📡 Detection & Monitoring
Log Indicators:
- Unexpected NFS service crashes in Event Logs
- Suspicious process creation from NFS-related executables
- Failed authentication attempts to NFS shares
Network Indicators:
- Unusual traffic to port 2049 from unexpected sources
- NFS protocol anomalies or malformed packets
SIEM Query:
source="windows" AND (event_id=7034 OR event_id=1000) AND process_name="*nfs*" OR destination_port=2049 AND protocol="TCP"