CVE-2020-1388: Windows 10 Privilege Escalation Vulnerability

CVE-2020-1388 Overview

An elevation of privilege vulnerability exists in the way that the psmsrv.dll handles objects in memory, commonly referred to as the 'Windows Elevation of Privilege Vulnerability'. This vulnerability allows an authenticated attacker with local access to execute code with elevated privileges, potentially gaining complete control over the affected system. This CVE ID is unique from CVE-2020-1392, CVE-2020-1394, and CVE-2020-1395.

Critical Impact

A local attacker who successfully exploits this vulnerability could execute arbitrary code with elevated privileges, potentially gaining SYSTEM-level access and complete control over the affected Windows system.

Affected Products

• Microsoft Windows 10 (multiple versions: 1607, 1709, 1803, 1809, 1903, 1909, 2004)
• Microsoft Windows Server 2016 (including versions 1903, 1909, 2004)
• Microsoft Windows Server 2019

Discovery Timeline

• July 14, 2020 - CVE-2020-1388 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-1388

Vulnerability Analysis

This elevation of privilege vulnerability stems from improper handling of objects in memory within the psmsrv.dll Windows system library. When the affected DLL processes certain memory objects, it fails to properly manage their lifecycle, creating an exploitable condition that allows attackers to elevate their privileges on the system.

The vulnerability requires local access to the target system and low-privilege authentication, making it a post-compromise escalation vector. An attacker who has already gained initial access to a Windows system through other means could leverage this vulnerability to escalate from a standard user account to SYSTEM-level privileges.

Root Cause

The root cause of CVE-2020-1388 lies in the improper memory object handling within psmsrv.dll. The DLL fails to correctly validate and manage object references during certain operations, leading to a condition where an attacker can manipulate memory state to gain elevated privileges. This type of memory management flaw is characteristic of object lifecycle vulnerabilities in Windows system components.

Attack Vector

The attack vector for CVE-2020-1388 is local, requiring the attacker to have authenticated access to the target system with at least low-level privileges. The exploitation does not require user interaction, allowing an attacker with initial foothold to silently escalate privileges.

An attacker would typically:

1. Gain initial access to a Windows system through phishing, credential theft, or other attack vectors
2. Execute a crafted application or script that triggers the memory handling flaw in psmsrv.dll
3. Manipulate the vulnerable memory handling to gain elevated privileges
4. Use the elevated privileges to install malware, access sensitive data, or move laterally through the network

Since this vulnerability affects a Windows system DLL, exploitation typically involves crafting specific API calls or system operations that trigger the flawed memory handling path. For technical implementation details, refer to the Microsoft Security Advisory CVE-2020-1388.

Detection Methods for CVE-2020-1388

Indicators of Compromise

• Unusual process creation events with unexpected parent-child relationships involving elevated privileges
• Suspicious activity involving psmsrv.dll loading patterns or memory access anomalies
• Unexpected privilege escalation events in Windows Security logs (Event ID 4672)
• Anomalous API calls to memory management functions from non-standard processes

Detection Strategies

• Monitor for privilege escalation attempts using Windows Event Logs, particularly Security Event ID 4672 (Special privileges assigned to new logon)
• Implement endpoint detection and response (EDR) solutions to detect suspicious memory manipulation behaviors
• Deploy behavioral analytics to identify unusual privilege elevation patterns on Windows systems
• Use SentinelOne's behavioral AI to detect exploitation attempts targeting Windows system DLLs

Monitoring Recommendations

• Enable advanced auditing for process creation and privilege use events in Windows Security Policy
• Configure SIEM alerts for privilege escalation patterns targeting Windows 10 and Windows Server systems
• Implement file integrity monitoring for critical Windows system DLLs including psmsrv.dll
• Establish baseline behaviors for privileged operations to detect anomalous activity

How to Mitigate CVE-2020-1388

Immediate Actions Required

• Apply the Microsoft security update released in July 2020 Patch Tuesday immediately to all affected Windows systems
• Prioritize patching systems with external exposure or those hosting sensitive data
• Implement the principle of least privilege to limit the impact of potential exploitation
• Review and restrict local user access on critical systems to reduce attack surface

Patch Information

Microsoft addressed this vulnerability as part of the July 2020 security updates. The official security patch is available through Windows Update and the Microsoft Update Catalog. Organizations should apply the update corresponding to their Windows version as documented in the Microsoft Security Advisory CVE-2020-1388.

Affected systems include:

• Windows 10 (all supported versions through 2004)
• Windows Server 2016 (all versions)
• Windows Server 2019

Workarounds

• Restrict local access to critical Windows systems to only authorized administrators
• Implement application whitelisting to prevent unauthorized applications from executing
• Use network segmentation to limit lateral movement if a system is compromised
• Deploy endpoint protection solutions with behavioral detection capabilities to identify exploitation attempts

# Verify patch installation status via PowerShell
Get-HotFix | Where-Object {$_.HotFixID -match "KB4565503|KB4565511|KB4565483|KB4558998"}

# Check Windows Update history for July 2020 security updates
wmic qfe list brief /format:table | findstr "2020-07"