CVE-2026-20843
📋 TL;DR
This vulnerability in Windows Routing and Remote Access Service (RRAS) allows authenticated attackers to escalate privileges on the local system. Attackers with valid credentials can exploit improper access controls to gain higher privileges than intended. This affects Windows systems with RRAS enabled.
💻 Affected Systems
- Windows Routing and Remote Access Service (RRAS)
📦 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 system compromise with administrative privileges, enabling installation of persistent malware, data theft, and lateral movement across the network.
Likely Case
Local privilege escalation allowing attackers to bypass security controls, access sensitive data, and maintain persistence on compromised systems.
If Mitigated
Limited impact with proper network segmentation, least privilege access, and monitoring in place, though local compromise still possible.
🎯 Exploit Status
Requires authenticated access but likely straightforward exploitation once authenticated. No public exploit code known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update Guide for specific KB numbers
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20843
Restart Required: Yes
Instructions:
1. Apply latest Windows security updates from Microsoft. 2. Install the specific patch for CVE-2026-20843. 3. Restart affected systems as required.
🔧 Temporary Workarounds
Disable RRAS if not needed
windowsDisable the Routing and Remote Access Service on systems where it's not required
sc config RemoteAccess start= disabled
sc stop RemoteAccess
Restrict RRAS access
windowsConfigure RRAS to only allow connections from authorized users and systems
🧯 If You Can't Patch
- Implement strict network segmentation to isolate systems with RRAS
- Enforce least privilege access and monitor for privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check if RRAS service is running and system has not applied the security patch for CVE-2026-20843Check Version:
wmic service where name='RemoteAccess' get name,state,pathnameVerify Fix Applied:
Verify Windows Update history shows the patch applied and RRAS service version is updated📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation events
- RRAS service configuration changes
- Failed authentication attempts followed by successful privilege escalation
Network Indicators:
- Unexpected RRAS connections from unauthorized sources
- Anomalous network routing changes
SIEM Query:
EventID=4672 OR EventID=4688 | where ProcessName contains 'rras' OR ServiceName contains 'RemoteAccess'