CVE-2022-26827
📋 TL;DR
This vulnerability allows an authenticated attacker to elevate privileges on Windows systems by exploiting a race condition in the File Server Resource Management Service. It affects Windows Server systems with the File Server Resource Manager role installed. Attackers could gain SYSTEM-level privileges on vulnerable servers.
💻 Affected Systems
- Windows Server
📦 What is this software?
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 11 by Microsoft
Windows 11 by Microsoft
Windows 7 by Microsoft
Windows 8.1 by Microsoft
Windows Rt 8.1 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with SYSTEM privileges, enabling installation of malware, data theft, lateral movement, and persistence mechanisms.
Likely Case
Privilege escalation from a standard user account to SYSTEM, allowing attackers to bypass security controls and access sensitive data.
If Mitigated
Limited impact due to proper patch management, network segmentation, and least privilege principles restricting initial access.
🎯 Exploit Status
Requires authenticated access and race condition exploitation. Proof-of-concept code has been published.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: April 2022 security updates (KB5012647 for Server 2019, KB5012596 for Server 2022)
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-26827
Restart Required: Yes
Instructions:
1. Apply April 2022 Windows Server security updates via Windows Update. 2. Alternatively, download and install KB5012647 (Server 2019) or KB5012596 (Server 2022) from Microsoft Update Catalog. 3. Restart the server after installation.
🔧 Temporary Workarounds
Disable FSRM Service
windowsTemporarily disable the File Server Resource Management Service if not required
sc stop FsRM
sc config FsRM start= disabled
🧯 If You Can't Patch
- Implement strict network segmentation to isolate file servers from other critical systems
- Apply least privilege principles and monitor for privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check if FSRM service is installed and running on Windows Server 2019/2022 without April 2022 patchesCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify KB5012647 (Server 2019) or KB5012596 (Server 2022) is installed via 'wmic qfe list' or 'Get-Hotfix'📡 Detection & Monitoring
Log Indicators:
- Event ID 4688 with FSRM process creation anomalies
- Unexpected privilege escalation events in security logs
Network Indicators:
- Unusual authentication patterns to file servers
- Anomalous process execution on FSRM servers
SIEM Query:
EventID=4688 AND (ProcessName="*fsrm*" OR CommandLine="*fsrm*") | stats count by host