CVE-2020-1013: Windows 10 Privilege Escalation Vulnerability

CVE-2020-1013 Overview

An elevation of privilege vulnerability exists in Microsoft Windows when processing group policy updates. This flaw allows an attacker who successfully exploits the vulnerability to potentially escalate permissions or perform additional privileged actions on the target machine.

To exploit this vulnerability, an attacker would need to launch a man-in-the-middle (MiTM) attack against the traffic passing between a domain controller and the target machine. Once positioned, an attacker could create a group policy to grant administrator rights to a standard user, effectively compromising the entire system's security posture.

Critical Impact

Successful exploitation enables attackers to elevate privileges from standard user to administrator through malicious group policy injection via MiTM attacks on domain controller communications.

Affected Products

• Microsoft Windows 10 (multiple versions including 1607, 1709, 1803, 1809, 1903, 1909, 2004)
• Microsoft Windows 7 SP1
• Microsoft Windows 8.1
• Microsoft Windows RT 8.1
• Microsoft Windows Server 2008 SP2 and R2 SP1
• Microsoft Windows Server 2012 and R2
• Microsoft Windows Server 2016 (including versions 1903, 1909, 2004)
• Microsoft Windows Server 2019

Discovery Timeline

• 2020-09-11 - CVE-2020-1013 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2020-1013

Vulnerability Analysis

This privilege escalation vulnerability stems from weaknesses in how Microsoft Windows handles authentication during group policy update processing. The vulnerability specifically affects the LDAP communication channel between domain-joined machines and their domain controllers.

When a Windows client requests group policy updates from a domain controller, the communication was not adequately protected by strong authentication mechanisms. This weakness allowed an attacker positioned in a man-in-the-middle position to intercept and manipulate the group policy response, injecting malicious policy configurations that the target machine would trust and apply.

The impact is significant because group policies govern critical security settings, user permissions, and system configurations across Windows environments. By manipulating these policies, an attacker can gain complete control over affected systems.

Root Cause

The root cause of CVE-2020-1013 lies in insufficient authentication enforcement for LDAP calls during group policy processing. Prior to the security update, certain calls over LDAP during group policy updates did not enforce Kerberos authentication, allowing attackers to potentially inject unauthorized group policy objects during the update process.

This authentication gap meant that while the overall communication might appear legitimate, specific operations within the group policy update workflow lacked the cryptographic verification necessary to ensure the integrity and authenticity of the policy data being received.

Attack Vector

The attack requires network access and the ability to intercept traffic between a target machine and its domain controller (man-in-the-middle position). The attacker must be able to position themselves on the network path, either through ARP spoofing, DNS poisoning, or physical network access.

Once in position, the attacker can intercept group policy update requests and inject malicious policies that grant elevated privileges. The attack does not require user interaction, making it particularly dangerous in enterprise environments where network segmentation may be insufficient.

The exploitation mechanism involves intercepting the LDAP traffic used for group policy retrieval, then modifying the response to include malicious group policy objects that grant the attacker administrative access on the target system.

Detection Methods for CVE-2020-1013

Indicators of Compromise

• Unexpected changes to group policy objects, particularly those affecting user privileges or security settings
• Anomalous LDAP traffic patterns between workstations and domain controllers
• Newly created administrator accounts or unexpected privilege escalations
• Signs of ARP spoofing or DNS poisoning on the network segment

Detection Strategies

• Monitor for group policy modification events (Event ID 5136, 5137) that occur outside normal administrative windows
• Implement network monitoring to detect potential MiTM attacks, including ARP anomalies and unauthorized DHCP responses
• Deploy endpoint detection solutions capable of identifying privilege escalation attempts following group policy updates
• Review Windows Event Logs for unusual group policy processing events (Event ID 1502, 1503)

Monitoring Recommendations

• Enable advanced auditing for Active Directory changes, particularly focusing on group policy object modifications
• Implement network segmentation monitoring to detect lateral movement attempts following privilege escalation
• Configure SIEM alerts for rapid succession of group policy changes affecting security-sensitive settings
• Monitor for authentication anomalies in domain controller logs that might indicate MiTM activity

How to Mitigate CVE-2020-1013

Immediate Actions Required

• Apply the Microsoft security update released in September 2020 immediately to all affected Windows systems
• Review current group policy objects for unauthorized modifications
• Implement network segmentation to limit potential MiTM attack surfaces
• Enable SMB signing and LDAP signing to strengthen authentication across domain communications

Patch Information

Microsoft has released a security update that addresses this vulnerability by enforcing Kerberos authentication for certain calls over LDAP during group policy processing. The patch is available through Windows Update and the Microsoft Update Catalog.

For detailed patch information and download links, refer to the Microsoft Security Advisory CVE-2020-1013.

Workarounds

• Enforce LDAP channel binding and signing via group policy settings to mitigate MiTM risks
• Implement IPsec between domain controllers and workstations to encrypt and authenticate network traffic
• Use network access control (NAC) to prevent unauthorized devices from accessing domain controller network segments
• Consider implementing 802.1X authentication on network switches to limit attacker access to network segments

# Enable LDAP signing via Group Policy
# Navigate to: Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > Security Options
# Set "Domain controller: LDAP server signing requirements" to "Require signing"
# Set "Network security: LDAP client signing requirements" to "Require signing"

# Verify LDAP signing is enabled via registry
reg query "HKLM\System\CurrentControlSet\Services\NTDS\Parameters" /v "LDAPServerIntegrity"
# Expected value: 2 (Require signing)