Micropatches released for SCF File NTLM Hash Disclosure Vulnerability (0day) - and Free Micropatches for it

 

 

While patching a SCF File NTLM hash disclosure issue on our security-adopted Windows versions, our researchers discovered a related vulnerability on all Windows Workstation and Server versions from Windows 7 and Server 2008 R2 to the latest Windows 11 v24H2 and Server 2025. The vulnerability allows an attacker to obtain user's NTLM credentials by having the user view a malicious file in Windows Explorer - e.g., by opening a shared folder or USB disk with such file, or viewing the Downloads folder where such file was previously automatically downloaded from attacker's web page.

Impact and attack scenarios of this issue are identical to that of a previously discovered 0day in URL files (subsequently patched by Microsoft), although the flaw is different here and to our knowledge not discussed in public before. 

[Update 04/09/2025] We were informed by George Hughey with MSRC Vulnerabilities & Mitigations that Microsoft recently brought a change to how SCF files are behaving. We have confirmed that on computers with January 2025 Windows Updates installed, Windows Explorer exhibits the behavior we're describing here only if the SCF file does not have the Mark of the Web. This means that attack scenarios on still-supported Windows versions like Windows 11 v24H2 do not include drive-by-downloaded SCF files, but do still include SCF files on network shared folders or USB drives. We'd like to thank George for sharing this information with us.

Note that while these types of vulnerabilities are not critical and their exploitability depends on several factors (e.g., the attacker either already being in the victim's network or having an external target like a public-facing Exchange server  to relay the stolen credentials to), they have been found to be used in actual attacks ([1][2]).

We reported this issue to Microsoft, and - as usual - issued micropatches for it that will remain free until Microsoft has provided an official fix.

We are withholding details on this vulnerability until Microsoft's fix becomes available to minimize the risk of malicious exploitation. 

This is the fourth 0day we have recently found and reported to Microsoft, after the Windows Theme file issue (subsequently patched by Microsoft as CVE-2025-21308), the Mark of the Web issue on Server 2012 (still a 0day without an official patch), and the URL File NTLM Hash Disclosure Vulnerability (subsequently patched by Microsoft as CVE-2025-21377).

In addition, the "EventLogCrasher" vulnerability, allowing an attacker to disable all Windows event logging on all domain computers (reported to Microsoft in January 2024 by security researcher Florian), is still waiting for an official patch so our patches for it are the only ones available.

There are also currently three NTLM-related publicly known "wont fix" vulnerabilities that Microsoft decided not to patch with 0patch patches available: PetitPotam, PrinterBug/SpoolSample and DFSCoerce. All of these are present on all latest fully updated Windows versions, and if your organization is using NTLM for any reason, it could be affected.

Currently, 40% of our users are using 0patch for protection against 0day and "wont fix" vulnerabilities, while others use 0patch for keeping their legacy Windows systems and Office versions secure with our security patches.

Micropatch Availability

Since this is a "0day" vulnerability with no official vendor fix available, we are providing our micropatches for free until such fix becomes available.

Micropatches were written for:

 Legacy Windows versions:

1. Windows 11 v21H2 - fully updated
2. Windows 10 v21H2 - fully updated
3. Windows 10 v21H1 - fully updated
4. Windows 10 v20H2 - fully updated
5. Windows 10 v2004 - fully updated
6. Windows 10 v1909 - fully updated
7. Windows 10 v1809 - fully updated
8. Windows 10 v1803 - fully updated
9. Windows 7 - fully updated with no ESU, ESU 1, ESU 2 or ESU 3
10. Windows Server 2012 - fully updated with no ESU or ESU 1
    
11. Windows Server 2012 R2 - fully updated with no ESU or ESU 1
12. Windows Server 2008 R2 - fully updated with no ESU, ESU 1, ESU 2, ESU 3 or ESU 4
    

 Windows versions still receiving Windows Updates:

1. Windows 11 v24H2 - fully updated   
2. Windows 11 v23H2 - fully updated
3. Windows 11 v22H2 - fully updated
4. Windows 10 v22H2 - fully updated
5. Windows Server 2025 - fully updated
   
6. Windows Server 2022 - fully updated
   
7. Windows Server 2019 - fully updated 
8. Windows Server 2016 - fully updated 
9. Windows Server 2012 fully updated with ESU 2
   
10. Windows Server 2012 R2 fully updated with ESU 2

 

Micropatches have already been distributed to, and applied on, all affected online computers with 0patch Agent in PRO or Enterprise accounts (unless Enterprise group settings prevented that).

Vulnerabilities like these get discovered on a regular basis, and attackers know about them all. If you're using Windows that aren't receiving official security updates anymore, 0patch will make sure these vulnerabilities won't be exploited on your computers - and you won't even have to know or care about these things.

If you're new to 0patch, create a free account in 0patch Central, start a free trial, then install and register 0patch Agent. Everything else will happen automatically. No computer reboot will be needed.

 

Did you know 0patch will security-adopt Windows 10 and Office 2016/2019 when they go out of support in October 2025, allowing you to keep using them for at least 5 more years? Read more about it here.

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