Nov 144 min read

The Future of NTLM in Windows: Why Legacy Protocols are a Cybersecurity Liability

The Rise of NTLM Vulnerabilities: Windows Themes Zero-Day and Microsoft’s Security Challenges Introduction Microsoft’s operating systems have long served as a backbone for global computing. Yet, due to the legacy protocols they support and the demands of backward compatibility, these systems remain a prime target for cyberattacks. A recent spate of zero-day vulnerabilities involving the NTLM (New Technology LAN Manager) protocol, specifically related to Windows Themes, has raised fresh concerns about NTLM's resilience. This article provides an in-depth analysis of NTLM vulnerabilities, Microsoft's response, and the broader implications for global cybersecurity. The History and Evolution of NTLM NTLM’s Origins and Purpose Originally developed in the early 1990s, NTLM was designed to facilitate secure user authentication over networks without transmitting plaintext passwords. The protocol quickly gained traction in both public and private sectors, underpinning authentication in Windows-based networks. However, over the years, NTLM's reliance on hashing and older security measures has become a liability in modern, threat-heavy environments. Protocol Year Introduced Primary Weaknesses Replacement NTLM Early 1990s Pass-the-hash, relay attacks Kerberos Kerberos Mid-2000s Ticket-granting targeted attacks Advanced Kerberos implementations Legacy Protocols and Their Modern Risks The integration of legacy protocols like NTLM within modern Windows environments presents a serious security risk. These protocols persist for compatibility reasons, as many organizations still rely on systems and applications that utilize NTLM. However, this backward compatibility often leaves these systems vulnerable to sophisticated modern attacks, posing risks that span across all currently supported Windows versions, from Windows 7 to Windows 11. The Mechanics of NTLM-Based Attacks How NTLM Works and Where It Fails NTLM functions by using hashed credentials for authentication, where hashed passwords are stored and transmitted in a way that avoids exposing the actual password. Unfortunately, NTLM’s reliance on hashes has made it vulnerable to two primary forms of attack: Pass-the-Hash Attacks: Attackers extract NTLM hashes and use them to impersonate the authenticated user. NTLM Relay Attacks: Attackers intercept the authentication process, relay the hash, and gain unauthorized access without needing the plaintext password. The persistence of NTLM within Windows ecosystems has created an expanding attack surface, as seen in recent vulnerabilities that attackers are actively exploiting. The Latest NTLM Zero-Day Vulnerabilities in Windows Themes Overview of Recent Vulnerabilities One of the latest critical vulnerabilities, discovered by Tomer Peled of Akamai, involves the manipulation of Windows Themes files to leak NTLM credentials remotely. When a malicious Windows Themes file is viewed in Explorer, it can prompt the system to send NTLM hashes to a remote server without user interaction. This vulnerability was initially addressed by Microsoft with patch CVE-2024-21320. However, researchers soon discovered that attackers could bypass this patch, leading to a new vulnerability, CVE-2024-38030, that continued to expose NTLM credentials. Bypass for Incomplete Security Patch Acros Security, through its 0patch service, stepped in to address the gaps left by Microsoft's patch. Acros Security CEO Mitja Kolsek shared that they created a generalized patch to block all Windows Themes files from triggering NTLM connections. “Instead of just fixing CVE-2024-38030, we developed a more comprehensive solution covering all execution paths that could lead to credential leaks,” Kolsek explained. Geopolitical Consequences: NTLM Exploits in Cyber Warfare A Case Study in Ukraine In one prominent case, attackers reportedly exploited an NTLM vulnerability, CVE-2024-43451, against Ukrainian government entities. According to a report by ClearSky, attackers employed phishing emails that redirected users to malicious theme files hosted on compromised Ukrainian government servers. These attacks, which allegedly originated from Russian threat actors, leveraged NTLM vulnerabilities to access sensitive government systems, highlighting the protocol’s attractiveness to cyber adversaries. Attack Vector Method Targeted Vulnerability Phishing and Theme Files Theme files triggering NTLM leaks CVE-2024-43451 Implications for Global Cybersecurity The Ukraine-focused attack reveals NTLM’s weaknesses as a viable pathway for cyber-espionage. As cyberattacks become increasingly politically motivated, NTLM vulnerabilities provide threat actors with a direct line to confidential data, raising concerns about NTLM's continued usage. Microsoft’s Response to NTLM Vulnerabilities Patch Tuesday and Emergency Updates In response to escalating threats, Microsoft has rolled out a series of patches in 2024 aimed at addressing NTLM vulnerabilities. Key Zero-Days Addressed in Patch Tuesday Microsoft’s October 2024 Patch Tuesday update addressed five zero-day vulnerabilities, including three critical remote code execution (RCE) vulnerabilities and two NTLM-based exploits. The updates represent Microsoft’s latest attempts to contain NTLM’s inherent risks while transitioning users toward more secure protocols. CVE-2024-43573 – A spoofing vulnerability in MSHTML that allowed attackers to gain unauthorized access. CVE-2024-43572 – A remote code execution vulnerability in Microsoft Management Console, where attackers could run arbitrary code through malicious MSC files. Potential Future of NTLM and Authentication Protocols in Windows Microsoft’s Efforts to Transition Beyond NTLM Microsoft has announced its intentions to phase out NTLM in future versions of Windows 11. This decision aligns with efforts to migrate legacy applications and protocols to more secure alternatives, such as Kerberos. Alternatives to NTLM and Their Advantages Transitioning away from NTLM would mitigate these vulnerabilities significantly. Advanced protocols like Kerberos provide better encryption and reduce the attack surface by requiring authentication tickets rather than transmitting hashed passwords across the network. Securing Windows Environments: Mitigation Strategies for Organizations Applying Available Patches and Micropatches Organizations should ensure they regularly update Windows systems with the latest patches. For those requiring immediate remediation, Acros Security’s 0patch provides temporary micropatches until official fixes are available. These unofficial patches are particularly useful for systems that rely on NTLM due to legacy software dependencies. Implementing Network Segmentation and Limiting NTLM Use Organizations can enhance security by limiting NTLM’s usage in favor of more secure protocols. This step should be accompanied by network segmentation practices to prevent lateral movement, as many NTLM exploits rely on moving through network environments to extract sensitive data. Conclusion The recent NTLM vulnerabilities underscore the broader challenges of maintaining security within Microsoft’s extensive user base, which still relies on legacy protocols. The persistence of NTLM and its vulnerabilities makes it an appealing target for cyber attackers, as demonstrated by incidents in Ukraine. As Microsoft pushes toward deprecating NTLM, organizations must prepare for a transition to more secure protocols while implementing immediate mitigation strategies. By staying informed and proactive, organizations can safeguard their systems, mitigating risks associated with legacy authentication protocols and evolving security threats.

Microsoft’s operating systems have long served as a backbone for global computing. Yet, due to the legacy protocols they support and the demands of backward compatibility, these systems remain a prime target for cyberattacks. A recent spate of zero-day vulnerabilities involving the NTLM (New Technology LAN Manager) protocol, specifically related to Windows Themes, has raised fresh concerns about NTLM's resilience. This article provides an in-depth analysis of NTLM vulnerabilities, Microsoft's response, and the broader implications for global cybersecurity.

The History and Evolution of NTLM

NTLM’s Origins and Purpose

Originally developed in the early 1990s, NTLM was designed to facilitate secure user authentication over networks without transmitting plaintext passwords. The protocol quickly gained traction in both public and private sectors, underpinning authentication in Windows-based networks. However, over the years, NTLM's reliance on hashing and older security measures has become a liability in modern, threat-heavy environments.

Protocol	Year Introduced	Primary Weaknesses	Replacement
NTLM	Early 1990s	Pass-the-hash, relay attacks	Kerberos
Kerberos	Mid-2000s	Ticket-granting targeted attacks	Advanced Kerberos implementations

Legacy Protocols and Their Modern Risks

The integration of legacy protocols like NTLM within modern Windows environments presents a serious security risk. These protocols persist for compatibility reasons, as many organizations still rely on systems and applications that utilize NTLM. However, this backward compatibility often leaves these systems vulnerable to sophisticated modern attacks, posing risks that span across all currently supported Windows versions, from Windows 7 to Windows 11.

The Mechanics of NTLM-Based Attacks

How NTLM Works and Where It Fails

NTLM functions by using hashed credentials for authentication, where hashed passwords are stored and transmitted in a way that avoids exposing the actual password. Unfortunately, NTLM’s reliance on hashes has made it vulnerable to two primary forms of attack:

Pass-the-Hash Attacks: Attackers extract NTLM hashes and use them to impersonate the authenticated user.
NTLM Relay Attacks: Attackers intercept the authentication process, relay the hash, and gain unauthorized access without needing the plaintext password.

The persistence of NTLM within Windows ecosystems has created an expanding attack surface, as seen in recent vulnerabilities that attackers are actively exploiting.

The Latest NTLM Zero-Day Vulnerabilities in Windows Themes

Overview of Recent Vulnerabilities

One of the latest critical vulnerabilities, discovered by Tomer Peled of Akamai, involves the manipulation of Windows Themes files to leak NTLM credentials remotely. When a malicious Windows Themes file is viewed in Explorer, it can prompt the system to send NTLM hashes to a remote server without user interaction. This vulnerability was initially addressed by Microsoft with patch CVE-2024-21320. However, researchers soon discovered that attackers could bypass this patch, leading to a new vulnerability, CVE-2024-38030, that continued to expose NTLM credentials.

Bypass for Incomplete Security Patch

Acros Security, through its 0patch service, stepped in to address the gaps left by Microsoft's patch. Acros Security CEO Mitja Kolsek shared that they created a generalized patch to block all Windows Themes files from triggering NTLM connections. “Instead of just fixing CVE-2024-38030, we developed a more comprehensive solution covering all execution paths that could lead to credential leaks,” Kolsek explained.

Geopolitical Consequences: NTLM Exploits in Cyber Warfare

A Case Study in Ukraine

In one prominent case, attackers reportedly exploited an NTLM vulnerability, CVE-2024-43451, against Ukrainian government entities. According to a report by ClearSky, attackers employed phishing emails that redirected users to malicious theme files hosted on compromised Ukrainian government servers. These attacks, which allegedly originated from Russian threat actors, leveraged NTLM vulnerabilities to access sensitive government systems, highlighting the protocol’s attractiveness to cyber adversaries.

Attack Vector	Method	Targeted Vulnerability
Phishing and Theme Files	Theme files triggering NTLM leaks	CVE-2024-43451

Implications for Global Cybersecurity

The Ukraine-focused attack reveals NTLM’s weaknesses as a viable pathway for cyber-espionage. As cyberattacks become increasingly politically motivated, NTLM vulnerabilities provide threat actors with a direct line to confidential data, raising concerns about NTLM's continued usage.

Microsoft’s Response to NTLM Vulnerabilities

Patch Tuesday and Emergency Updates

In response to escalating threats, Microsoft has rolled out a series of patches in 2024 aimed at addressing NTLM vulnerabilities.

Key Zero-Days Addressed in Patch Tuesday

Microsoft’s October 2024 Patch Tuesday update addressed five zero-day vulnerabilities, including three critical remote code execution (RCE) vulnerabilities and two NTLM-based exploits. The updates represent Microsoft’s latest attempts to contain NTLM’s inherent risks while transitioning users toward more secure protocols.

CVE-2024-43573 – A spoofing vulnerability in MSHTML that allowed attackers to gain unauthorized access.
CVE-2024-43572 – A remote code execution vulnerability in Microsoft Management Console, where attackers could run arbitrary code through malicious MSC files.

Potential Future of NTLM and Authentication Protocols in Windows

Microsoft’s Efforts to Transition Beyond NTLM

Microsoft has announced its intentions to phase out NTLM in future versions of Windows 11. This decision aligns with efforts to migrate legacy applications and protocols to more secure alternatives, such as Kerberos.

Alternatives to NTLM and Their Advantages

Transitioning away from NTLM would mitigate these vulnerabilities significantly. Advanced protocols like Kerberos provide better encryption and reduce the attack surface by requiring authentication tickets rather than transmitting hashed passwords across the network.

Securing Windows Environments: Mitigation Strategies for Organizations

Applying Available Patches and Micropatches

Organizations should ensure they regularly update Windows systems with the latest patches. For those requiring immediate remediation, Acros Security’s 0patch provides temporary micropatches until official fixes are available. These unofficial patches are particularly useful for systems that rely on NTLM due to legacy software dependencies.

Implementing Network Segmentation and Limiting NTLM Use

Organizations can enhance security by limiting NTLM’s usage in favor of more secure protocols. This step should be accompanied by network segmentation practices to prevent lateral movement, as many NTLM exploits rely on moving through network environments to extract sensitive data.

Conclusion

The recent NTLM vulnerabilities underscore the broader challenges of maintaining security within Microsoft’s extensive user base, which still relies on legacy protocols. The persistence of NTLM and its vulnerabilities makes it an appealing target for cyber attackers, as demonstrated by incidents in Ukraine. As Microsoft pushes toward deprecating NTLM, organizations must prepare for a transition to more secure protocols while implementing immediate mitigation strategies. By staying informed and proactive, organizations can safeguard their systems, mitigating risks associated with legacy authentication protocols and evolving security threats.