Overview of the Hafnium Microsoft Hack
This article discusses a Microsoft Exchange Server vulnerability that has affected 30,000+ servers worldwide.
A zero-day vulnerability affecting on-premises Microsoft Exchange Servers.
Microsoft 365 (Cloud-based Exchange) is not affected.
The exploit allows attackers to access email accounts and install malware for long-term access.
Investigating and patching CVE-2021-26855 in on-premise Microsoft Exchange server
✅ Automatic Check
- Download Test-ProxyLogon script from GitHub.
- Run it in Exchange Management Shell:
Get-ExchangeServer | Test-ProxyLogon -OutPath C:\Logs
If the results indicate compromise, proceed to mitigation.
Manual Check
- Look for specific files in these directories:
C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\C:\inetpub\wwwroot\aspnet_client\
- If these files exist and were not created by you, the server is likely compromised.
Patching The Vulnerability
Temporary Fix
- Download Microsoft’s mitigation script and apply it to the affected server:
.\ExchangeMitigation.ps1 -Server FQDN
- This is a temporary measure and does not fully fix the issue.
Permanent Fix (Recommended)
- Apply the latest Microsoft security patches for your Exchange Server version:
- 2010, 2013, 2016, 2019: Download MSP patch files from Microsoft’s website.
- Run the update via Command Prompt:
msiexec /update C:\Path\to\Patch.msp
Penetration Testing (For Security Analysts)
- If you are testing a client’s system remotely, use an Nmap script:
nmap -sV -A --script exchange-vuln.nse <Target_IP>
This helps determine if the Exchange Server is still vulnerable without direct access.
Final Recommendations
- Patch your system ASAP to prevent cyberattacks.
- Enable automatic updates to stay protected from future exploits.
- If compromised, conduct a full forensic analysis and remove malware.
Video Walkthrough
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