CVE-2021-1702
📋 TL;DR
CVE-2021-1702 is an elevation of privilege vulnerability in Windows Remote Procedure Call (RPC) Runtime that allows authenticated attackers to execute code with SYSTEM privileges. This affects Windows systems where an attacker has local access or can authenticate to the target system. The vulnerability requires the attacker to have some level of initial access to exploit.
💻 Affected Systems
- Microsoft Windows
📦 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 10 by Microsoft
Windows 7 by Microsoft
Windows 8.1 by Microsoft
Windows Rt 8.1 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
An attacker gains full SYSTEM privileges on a Windows system, enabling complete control, credential theft, lateral movement, and persistence establishment.
Likely Case
Privilege escalation from a standard user or service 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 preventing initial access.
🎯 Exploit Status
Exploit code has been publicly released. Requires authenticated access but is relatively simple to execute once initial access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: January 2021 security updates (KB4598242, KB4598229, etc.)
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-1702
Restart Required: Yes
Instructions:
1. Apply January 2021 Windows security updates via Windows Update. 2. For enterprise environments, deploy updates through WSUS or SCCM. 3. Restart systems after patch installation.
🔧 Temporary Workarounds
Restrict RPC access
windowsLimit RPC access to trusted systems only using Windows Firewall rules
New-NetFirewallRule -DisplayName "Block RPC" -Direction Inbound -Protocol TCP -LocalPort 135 -Action Block
Implement least privilege
windowsEnsure users and service accounts have minimal privileges required
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems
- Enable Windows Defender Exploit Guard and Application Control
🔍 How to Verify
Check if Vulnerable:
Check Windows version and if January 2021 security updates are installed via 'systeminfo' commandCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify KB4598242 or relevant January 2021 security update is installed via 'wmic qfe list' or PowerShell 'Get-HotFix'📡 Detection & Monitoring
Log Indicators:
- Event ID 4688 with parent process svchost.exe spawning unexpected processes
- Unusual RPC service activity in Windows Security logs
Network Indicators:
- Unusual RPC connections to port 135 from unexpected sources
SIEM Query:
source="windows" event_id=4688 parent_process_name="svchost.exe" process_name="cmd.exe" OR process_name="powershell.exe"