What is a zero-day exploit?
A zero-day is a computer-software vulnerability that was previously unknown to those who should be concerned about its mitigation, such as the target software’s vendor.
What is Follina Zero-Day RCE?
Follina is a nickname given to the discovered vulnerability CVE-2022-30190. Follina is exploiting Microsoft Windows Support Diagnostics Tool (MSDT) to get Remote Code Execution.
How does the exploit work?
Follina uses Word’s external link to load the HTML and then uses ms-msdt scheme to execute PowerShell code. Don’t confuse this attack with macro attack as it’s not. Macros can be turned off and this exploit will still be possible to execute. In simple terms the exploit path looks like this:
Malicious document is received ->
-> Document references regular-looking URL (that will get downloaded) ->
-> URL references an HTML file containing JavaScript code ->
-> JavaScript references and URL with “ms-msdt:” identifier instead of “https:” ->
-> “ms-msdt:” launches Microsoft Support Diagnostics Tool (MSDT) ->
-> Referenced URL is supplying commands to MSDT causing it to run untrusted code.
Is My Windows PC Vulnerable to the Follina Exploit?
On its security update guide page, Microsoft has listed 41 versions of Windows that are vulnerable to Follina CVE-2022-30190 vulnerability. It includes Windows 7, Windows 8.1, Windows 10, Windows 11, and even Windows Server editions. Check out the complete list of affected versions below:
- Windows 10 Version 1607 for 32-bit Systems
- Windows 10 Version 1607 for x64-based Systems
- Windows 10 Version 1809 for 32-bit Systems
- Windows 10 Version 1809 for ARM64-based Systems
- Windows 10 Version 1809 for x64-based Systems
- Windows 10 Version 20H2 for 32-bit Systems
- Windows 10 Version 20H2 for ARM64-based Systems
- Windows 10 Version 20H2 for x64-based Systems
- Windows 10 Version 21H1 for 32-bit Systems
- Windows 10 Version 21H1 for ARM64-based Systems
- Windows 10 Version 21H1 for x64-based Systems
- Windows 10 Version 21H2 for 32-bit Systems
- Windows 10 Version 21H2 for ARM64-based Systems
- Windows 10 Version 21H2 for x64-based Systems
- Windows 10 for 32-bit Systems
- Windows 10 for x64-based Systems
- Windows 11 for ARM64-based Systems
- Windows 11 for x64-based Systems
- Windows 7 for 32-bit Systems Service Pack 1
- Windows 7 for x64-based Systems Service Pack 1
- Windows 8.1 for 32-bit systems
- Windows 8.1 for x64-based systems
- Windows RT 8.1
- Windows Server 2008 R2 for x64-based Systems Service Pack 1
- Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)
- Windows Server 2008 for 32-bit Systems Service Pack 2
- Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
- Windows Server 2008 for x64-based Systems Service Pack 2
- Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
- Windows Server 2012
- Windows Server 2012 (Server Core installation)
- Windows Server 2012 R2
- Windows Server 2012 R2 (Server Core installation)
- Windows Server 2016
- Windows Server 2016 (Server Core installation)
- Windows Server 2019
- Windows Server 2019 (Server Core installation)
- Windows Server 2022
- Windows Server 2022 (Server Core installation)
- Windows Server 2022 Azure Edition Core Hotpatch
- Windows Server, version 20H2 (Server Core Installation)
Solutions?
Disable MSDT URL Protocol to Protect Windows from Follina Vulnerability
Microsoft has provided a quick and simple workaround to prevent attacks done by this exploit. The fix is to delete registry entry for search-ms, thus disabling MSDT URL protocol.
- Run a Command Prompt as Administrator.
- Back-up the registry key by entering command – “reg export HKEY_CLASSES_ROOT\ms-msdt filename”.
- Execute the command “reg delete HKEY_CLASSES_ROOT\ms-msdt /f”.
- To undo the workaround simply import the backed-up registry key
- Execute the command “reg import filename”
Guidance for CVE-2022-30190 Microsoft Support Diagnostic Tool Vulnerability
