⚠️ Critical Update for All Windows Admins & Security Teams
A new 0-click NTLM credential leakage vulnerability has been discovered that bypasses Microsoft’s previous patch — putting Windows systems back in the attacker’s crosshairs.
🔍 What’s the Threat?
- 0-click = The victim doesn’t have to click anything. Merely viewing a crafted file (like an email, shared doc, or SMB resource) can trigger the exploit.
- The flaw enables NTLM authentication requests to be coerced to an attacker-controlled server.
- Once intercepted, NTLM hashes can be cracked offline or relayed to escalate privileges, pivot laterally, or access sensitive resources.
- This new technique evades Microsoft’s previous mitigations for similar NTLM leak vulnerabilities.
🛠️ How It Works
- Malicious resource reference (UNC path, embedded link, crafted LNK file) points to attacker’s SMB/WebDAV server.
- Windows automatically attempts NTLM auth when resolving that path.
- Attacker harvests the NTLMv2 hash.
- Offline cracking or NTLM relay is used to impersonate the user or gain higher privileges.
🎯 Why It’s Dangerous
- Works on fully patched Windows builds that applied Microsoft’s earlier NTLM leak fix.
- No user interaction needed = stealthy exploitation.
- Effective for internal breaches and red team operations.
- Can be chained with Relay to Active Directory Certificate Services (ADCS) or other lateral movement techniques.
🛡️ CyberDudeBivash Countermeasures
1️⃣ Immediate Mitigations
- Block outbound SMB (TCP 445) and WebDAV (TCP 80/443) to untrusted IP ranges.
- Disable NTLM where possible: Group Policy → Security Options → “Network security: Restrict NTLM.”
- For high-value accounts, enforce Kerberos-only auth.
2️⃣ Monitoring & Detection
- SIEM/EDR alerts for:
- Outbound SMB connections to non-whitelisted destinations.
- NTLM authentication attempts to unfamiliar hosts.
- Hunt for suspicious UNC paths in logs.
3️⃣ Hardening
- Apply Microsoft’s latest advisories & registry-level mitigations for NTLM leak scenarios.
- Disable WebClient service if not required.
- Isolate high-privilege accounts on separate admin workstations (PAWs).
💬 Over to You
How many of you still see NTLM enabled in production? And do you have SMB egress filtering in place right now?
Let’s talk in the comments — this is a wake-up call for every Windows environment.
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