The recent discovery of a critical vulnerability in Windows File Explorer—a flaw that enables attackers to harvest NTLM hashed passwords without any user interaction—has sent shockwaves through the Windows community. Operating under the moniker CVE-2025-24071, this exploit, infamously dubbed the "NTLM Hash Leak via RAR/ZIP Extraction," capitalizes on the trusted file extraction process that lies at the heart of Windows’ everyday operation.
A specially crafted .library-ms file, when extracted, can include XML tags that redirect Windows to an attacker-controlled SMB server. The operating system, trusting the file’s contents, attempts to initiate an NTLM authentication handshake to resolve the SMB path. This seemingly benign process inadvertently transmits NTLM hash credentials over the network, leaving users vulnerable to remote capture without even a hint of suspicious activity.
• Attackers craft a malicious .library-ms file inside a compressed archive.
• The file includes XML tags that point directly to an attacker-controlled SMB server (for example, \192.168.1.116\shared).
• Upon extraction, Windows Explorer automatically accesses the SMB path to resolve the location details.
• This access triggers an NTLM authentication handshake, during which Windows inadvertently sends the user's NTLM hash to the attacker's server.
What makes this vulnerability particularly insidious is that it requires no user interaction beyond the mere act of extracting the archive. The automatic nature of the file processing means that even vigilant users, accustomed to regularly handling compressed files, could be unknowingly leaking sensitive credentials.
• Pass-the-hash attacks – where an attacker reuses stolen hash credentials to gain unauthorized access to other systems.
• Offline hash cracking – allowing adversaries to run brute-force attacks on obtained hashes to eventually recover plain text passwords.
With a CVSS score of 7.5, this vulnerability is categorized as a significant risk, demanding immediate action. The possibility of bypassing user authentication without any visible indicators places this flaw in a particularly dangerous category. For enterprises and individual users alike, the ripple effect of such an exploit could lead to widespread data breaches and network compromises.
Adding further fuel to the fire, a notorious threat actor known as “Krypt0n” has reportedly offered the exploit for sale on dark web forums. In discussion threads, Krypt0n explained that the target server is often set up locally, sometimes on a VPS. After configuring the exploit with specific network details (IP address, share, etc.), any access via Explorer or even an innocent click on a shared folder triggers an automatic redirect that sends the user’s NTLM hash to the attacker’s server. This commercial interest in the exploit underscores its potential impact and the urgency for immediate countermeasures.
For Windows users and IT administrators, the key recommendations are:
• Immediately apply the critical patch released on March 11, 2025.
• Ensure that your system is running the latest security updates to preclude exploitation from this and similar vulnerabilities.
• Consider disabling NTLM authentication where possible, especially on systems handling sensitive credentials.
• Implement additional security measures such as SMB signing to reduce the risk of unauthorized hash capture.
• Windows 10 (versions 1607, 1809, 21H2, 22H2, 23H2, and 24H2)
• Windows 11 (versions 23H2 and 24H2)
• Various iterations of Windows Server
This extensive range serves as a stark reminder that even widely used and time-tested Windows features can harbor unseen risks. For enterprise environments where NTLM authentication remains prevalent, the exploit's potential for lateral movement across networks poses a particular challenge. The incident not only highlights vulnerabilities in Windows File Explorer but also exposes the inherent limitations of NTLM—a protocol long criticized for its security weaknesses.
This episode also encourages a critical look at automated processing in operating systems. As defenses against cyber threats become increasingly sophisticated, attackers are similarly advancing their methods, often targeting the convenience features built into systems. Windows users and IT administrators are thus urged to balance usability with security, ensuring that automated processes do not become inadvertent channels for cyberattacks.
Key reflections for the IT community include:
• The need for a gradual retirement or hardening of dated authentication methods like NTLM.
• Encouraging a culture of proactive vulnerability management, where regular patching is complemented by additional security controls such as network segmentation and enhanced monitoring.
• Reinforcing the importance of user education, so individuals are aware of the risks even in everyday actions like file extraction.
For all Windows users, the message is clear: keep your systems updated, consider tightening your authentication methods, and remain cognizant of the subtle yet significant ways that everyday tasks can expose your data to risk. In an era where cyber threats evolve as rapidly as the technology they target, staying informed and proactive is not just advisable—it’s essential.
Source: Evrim Ağacı Critical Windows Vulnerability Exposes NTLM Passwords
Background and Discovery
In mid-March 2025, security researchers identified and publicly reported the vulnerability, revealing an alarming attack vector. Traditionally, Windows File Explorer is designed to simplify your interaction with files and folders. However, it appears that its convenience harbors a dangerous secret: when processing compressed archives such as RAR or ZIP files, Windows automatically extracts .library-ms files—XML-based configuration files that define library locations. These files, normally seen as helpful, can be weaponized by attackers.A specially crafted .library-ms file, when extracted, can include XML tags that redirect Windows to an attacker-controlled SMB server. The operating system, trusting the file’s contents, attempts to initiate an NTLM authentication handshake to resolve the SMB path. This seemingly benign process inadvertently transmits NTLM hash credentials over the network, leaving users vulnerable to remote capture without even a hint of suspicious activity.
How the Exploit Works
The exploitation mechanism behind CVE-2025-24071 exploits a core feature built into Windows Explorer for processing library definitions. Here’s the breakdown:• Attackers craft a malicious .library-ms file inside a compressed archive.
• The file includes XML tags that point directly to an attacker-controlled SMB server (for example, \192.168.1.116\shared).
• Upon extraction, Windows Explorer automatically accesses the SMB path to resolve the location details.
• This access triggers an NTLM authentication handshake, during which Windows inadvertently sends the user's NTLM hash to the attacker's server.
What makes this vulnerability particularly insidious is that it requires no user interaction beyond the mere act of extracting the archive. The automatic nature of the file processing means that even vigilant users, accustomed to regularly handling compressed files, could be unknowingly leaking sensitive credentials.
Technical Implications and Risks
From a security standpoint, the exposed NTLM hashes can be leveraged in several nefarious ways. Among the most alarming attack methods are:• Pass-the-hash attacks – where an attacker reuses stolen hash credentials to gain unauthorized access to other systems.
• Offline hash cracking – allowing adversaries to run brute-force attacks on obtained hashes to eventually recover plain text passwords.
With a CVSS score of 7.5, this vulnerability is categorized as a significant risk, demanding immediate action. The possibility of bypassing user authentication without any visible indicators places this flaw in a particularly dangerous category. For enterprises and individual users alike, the ripple effect of such an exploit could lead to widespread data breaches and network compromises.
A Peek into the Proof-of-Concept and Malicious Interest
Not long after the vulnerability’s disclosure, a security researcher known by the pseudonym “0x6rss” published a proof-of-concept exploit on GitHub. The PoC, implemented in Python, demonstrates how straightforward it is to generate the malicious .library-ms file. With a simple command—python poc.py—the process is set in motion, lowering the barrier for potential attackers who might lack advanced programming skills.Adding further fuel to the fire, a notorious threat actor known as “Krypt0n” has reportedly offered the exploit for sale on dark web forums. In discussion threads, Krypt0n explained that the target server is often set up locally, sometimes on a VPS. After configuring the exploit with specific network details (IP address, share, etc.), any access via Explorer or even an innocent click on a shared folder triggers an automatic redirect that sends the user’s NTLM hash to the attacker’s server. This commercial interest in the exploit underscores its potential impact and the urgency for immediate countermeasures.
Microsoft’s Swift Response and Patch Recommendations
Recognizing the gravity of the situation, Microsoft reacted quickly. As part of their scheduled March 2025 Patch Tuesday updates on the 11th, a critical patch addressing CVE-2025-24071 was released. This update is designed to plug the exploit's loophole and reinforce the security of Windows Explorer against similar attacks.For Windows users and IT administrators, the key recommendations are:
• Immediately apply the critical patch released on March 11, 2025.
• Ensure that your system is running the latest security updates to preclude exploitation from this and similar vulnerabilities.
• Consider disabling NTLM authentication where possible, especially on systems handling sensitive credentials.
• Implement additional security measures such as SMB signing to reduce the risk of unauthorized hash capture.
Affected Systems and Broader Impact
The scope of this vulnerability spans across multiple versions of Microsoft’s operating systems. Affected platforms include:• Windows 10 (versions 1607, 1809, 21H2, 22H2, 23H2, and 24H2)
• Windows 11 (versions 23H2 and 24H2)
• Various iterations of Windows Server
This extensive range serves as a stark reminder that even widely used and time-tested Windows features can harbor unseen risks. For enterprise environments where NTLM authentication remains prevalent, the exploit's potential for lateral movement across networks poses a particular challenge. The incident not only highlights vulnerabilities in Windows File Explorer but also exposes the inherent limitations of NTLM—a protocol long criticized for its security weaknesses.
Industry Implications and Long-Term Considerations
The exploitation of CVE-2025-24071 forces us to confront broader questions about the security architecture of foundational Windows components. NTLM, while historically instrumental in Windows authentication, has repeatedly been shown to suffer from vulnerabilities that can be exploited remotely. The current incident is a reminder that legacy protocols must be continually scrutinized and updated—or even disabled—when more secure alternatives exist.This episode also encourages a critical look at automated processing in operating systems. As defenses against cyber threats become increasingly sophisticated, attackers are similarly advancing their methods, often targeting the convenience features built into systems. Windows users and IT administrators are thus urged to balance usability with security, ensuring that automated processes do not become inadvertent channels for cyberattacks.
Key reflections for the IT community include:
• The need for a gradual retirement or hardening of dated authentication methods like NTLM.
• Encouraging a culture of proactive vulnerability management, where regular patching is complemented by additional security controls such as network segmentation and enhanced monitoring.
• Reinforcing the importance of user education, so individuals are aware of the risks even in everyday actions like file extraction.
Final Thoughts
The discovery of CVE-2025-24071 is a stark reminder of the delicate balance between convenience and security in today’s digital landscape. With automated features that streamline file management, Windows users inadvertently expose themselves to sophisticated attacks that can compromise critical login credentials. While Microsoft’s prompt patch release is reassuring, the incident underscores the need for ongoing vigilance and the continual reassessment of legacy security protocols.For all Windows users, the message is clear: keep your systems updated, consider tightening your authentication methods, and remain cognizant of the subtle yet significant ways that everyday tasks can expose your data to risk. In an era where cyber threats evolve as rapidly as the technology they target, staying informed and proactive is not just advisable—it’s essential.
Source: Evrim Ağacı Critical Windows Vulnerability Exposes NTLM Passwords
