NTLM Vulnerability in Windows: 0patch Releases Critical Micropatch

Windows security aficionados, brace yourselves for another deep dive into the often murky realm of legacy authentication protocols. An unofficial NTLM security patch from 0patch is now available for Windows 11 (v24H2), Windows Server 2025, and several versions of Windows 10. This update comes hot on the heels of a similar micropatch issued in December 2024, and it targets a vulnerability that could potentially give attackers access to your NTLM credentials.

The NTLM Vulnerability Unveiled​

The vulnerability was discovered during the patching of a SCF File NTLM hash disclosure. In this context, an attacker can exploit the flaw simply by enticing a user to view a malicious file in Windows Explorer. This could occur when browsing a shared folder, inserting a compromised USB drive, or even by having an unsuspecting user open the Downloads folder—where sometimes files are automatically deposited from compromised web pages.
Key points of the vulnerability:

• It stems from how NTLM hashes are handled in SCF files.
• The flaw could expose NTLM credentials, putting users at risk.
• The vulnerability affects a wide range of Windows editions from Windows 7 and Server 2008 R2 up to the latest iterations of Windows 11 and Windows Server.

Microsoft, which has long acknowledged the security limitations of NTLM (New Technology LAN Manager), had earlier assigned a CVE number (CVE-2025-21377) for a previous instance of the vulnerability. Despite these past concerns, NTLM remains in use even as industry experts advocate for more secure authentication methods.

Affected Windows Versions​

0patch’s new micropatch extends its coverage to nearly every active Windows edition. The patch has been crafted for two major groups of versions: legacy systems and those still actively receiving updates.

Legacy Windows Versions​

The patch now benefits systems including:

• Windows 11 v21H2 (fully updated)
• Windows 10 versions v21H2, v21H1, v20H2, v2004, v1909, v1809, and v1803 (fully updated)
• Windows 7 (fully updated, without ESU, ESU 1, ESU 2, or ESU 3)
• Windows Server 2012 and Server 2012 R2 (fully updated without ESU or ESU 1)
• Windows Server 2008 R2 (fully updated across all ESU levels)

Systems Still Receiving Windows Updates​

The new micropatch covers more recent editions as well, such as:

• Windows 11 v24H2, v23H2, and v22H2 (all fully updated)
• Windows 10 v22H2 (fully updated)
• Windows Server 2025, Server 2022, Server 2019, and Server 2016 (fully updated)
• Windows Server 2012 and Server 2012 R2 (fully updated with ESU 2)

The inclusion of Windows Server 2025 is a notable update, as it wasn’t part of the initial list of affected systems, underscoring the widespread nature of this vulnerability.

Understanding the Patch and Its Implications​

0patch’s approach has always been to deliver micropatches that address specific security issues without the need for a full-fledged operating system update—a boon for enterprise environments where immediate downtime is a luxury and often an impossibility.
Here’s how the patch works:

• It prevents the disclosure of NTLM hashes from SCF files before the malicious chain of events can occur.
• Even though it addresses a niche scenario (viewing a malicious file), this patch is a clear sign that even minor flaws are being taken seriously in an era of ever-sophisticated cyberattacks.

The broader implications are significant:

• The reminder that NTLM remains a weak link: Microsoft has repeatedly indicated that NTLM is an outdated protocol. Its “death” has been declared, and users are encouraged to shift toward modern, secure alternatives like Kerberos.
• User awareness is a must: The simple act of viewing a file in Windows Explorer can, under the right (or wrong) conditions, lead to credential disclosure. This reinforces the importance of best practices in file handling and network security.

Expert Analysis: The Future of NTLM and Windows Security​

If you’ve been following the evolution of authentication methods on Windows, this latest patch should not come as a complete surprise. NTLM has long been a fixture in the Microsoft ecosystem, even as its weaknesses become ever more apparent. Here are a few reflective points for the discerning IT professional:

• Why does NTLM still linger? Despite its vulnerabilities, NTLM is deeply rooted in legacy systems and backward compatibility concerns. However, the growing body of evidence, highlighted by incidents like this one, strongly suggests that continuing to rely on NTLM is akin to leaving a door slightly ajar in an increasingly perilous neighborhood.
• How should organizations prepare? Enterprises should evaluate their reliance on NTLM, implementing modern authentication protocols wherever possible. This micropatch is a necessary safety net—but it is not a substitute for a strategic overhaul of authentication policies.
• What about personal users? For individual users relying on standard Windows Update policies, the patch underscores the importance of not taking system security for granted. Regular updates and vigilance are key to mitigating these threats.

For those who seek extra security without waiting for an official Microsoft patch, 0patch Central offers these free micropatches. While not officially sanctioned by Microsoft, these patches play a crucial role in providing interim protection as the industry slowly moves away from legacy protocols.

Best Practices and Moving Forward​

Given the evolving landscape of cybersecurity threats, here are some actionable recommendations for both home users and IT administrators:

• Review your authentication protocols: If NTLM is still in use within your network, consider moving to more robust alternatives like Kerberos where feasible.
• Apply updates proactively: Ensure that you are running the latest fully updated versions of Windows and Windows Server. Even unofficial patches like those provided by 0patch can serve as a temporary shield against exploitation.
• Educate users: Remind everyone in your organization about the risks of opening files from unknown or untrusted sources—especially in shared network environments.
• Monitor security advisories: Keep a close eye on both Microsoft’s security bulletins and third-party advisories. The cybersecurity landscape is evolving, and staying informed is your first line of defense.

Conclusion​

The emergence of this new NTLM vulnerability patch is a wake-up call to all Windows users. While unofficial patches like those from 0patch serve an important role in bolstering security, they also highlight the need for a broader shift away from outdated protocols. As Microsoft continues to push its vision of a more secure operating environment—with NTLM’s eventual obsolescence looming on the horizon—device users across the board must take proactive steps to secure their systems.
In the dynamic and yet unforgiving world of Windows security, keeping abreast of both official and unofficial updates is not just prudent; it is essential. Stay vigilant, stay updated, and consider this the perfect moment to reexamine your network’s authentication framework.

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Source: Neowin Another unofficial NTLM security patch out for Windows 11 24H2, Server 2025, and Windows 10