CVE-2019-1177
📋 TL;DR
CVE-2019-1177 is a local privilege escalation vulnerability in Windows' rpcss.dll component. An authenticated attacker could exploit this to execute arbitrary code with SYSTEM privileges. This affects Windows systems where an attacker has local access.
💻 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 the compromised system, enabling complete control, persistence, lateral movement, and data exfiltration.
Likely Case
Malware or malicious users escalate privileges from standard user accounts to SYSTEM to bypass security controls and install persistent backdoors.
If Mitigated
With proper patch management and least privilege principles, impact is limited to isolated systems with no lateral movement capability.
🎯 Exploit Status
Exploitation requires local authenticated access. Proof-of-concept code has been publicly available since disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: August 2019 security updates (KB4512508 for Windows 10 1903, KB4512534 for Windows 10 1909)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1177
Restart Required: Yes
Instructions:
1. Apply August 2019 Windows security updates via Windows Update. 2. For enterprise environments, deploy through WSUS or SCCM. 3. Restart systems after patch installation.
🔧 Temporary Workarounds
Restrict local user privileges
windowsImplement least privilege by removing local administrator rights from standard users
Application control policies
windowsUse AppLocker or Windows Defender Application Control to block unauthorized applications
🧯 If You Can't Patch
- Implement strict application whitelisting to prevent execution of unauthorized binaries
- Deploy endpoint detection and response (EDR) solutions to detect privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check Windows version with 'winver' and verify it's Windows 10 1903 or 1909 without August 2019 updatesCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify KB4512508 (1903) or KB4512534 (1909) is installed via 'wmic qfe list' or PowerShell 'Get-HotFix -Id KB4512508'📡 Detection & Monitoring
Log Indicators:
- Windows Security Event ID 4688 (process creation) showing unexpected SYSTEM privilege processes
- Event ID 4672 (special privileges assigned)
Network Indicators:
- Unusual outbound connections from SYSTEM context processes
SIEM Query:
EventID=4688 AND NewProcessName="*" AND SubjectUserName!="SYSTEM" AND TokenElevationType="%%1937"