CVE-2024-26180 - Secure Boot Security Feature Bypass Vulnerability Explained

In early 2024, security researchers revealed a new critical vulnerability affecting Windows Secure Boot – CVE-2024-26180. This flaw allows attackers to bypass Secure Boot protections, which are supposed to ensure that only trusted code loads during system startup. In this article, we break down what CVE-2024-26180 is, how it works, how attackers can exploit it, and what you can do to protect your devices.

What is Secure Boot?

Secure Boot is a security feature available in most modern computers with UEFI firmware. It helps prevent unauthorized software (like bootkits and rootkits) from loading when your device starts up. If Secure Boot is compromised, an attacker could install persistent malware that loads before the operating system or antivirus software starts.

CVE-2024-26180 — The Bypass in a Nutshell

CVE-2024-26180 is a Secure Boot security feature bypass vulnerability discovered by Microsoft. The flaw allows attackers who already have administrative access to a machine to install malicious bootloaders, UEFI rootkits, or disable Secure Boot checks. This gives them control over the boot process, making malware almost invisible and undetectable.

Official Microsoft Reference

- Microsoft Security Response Center: CVE-2024-26180 | Secure Boot Security Feature Bypass Vulnerability

Step 1: Attacker Gets Local Admin Rights

Attackers must get admin access on the target machine — for example, through phishing, privilege escalation, or by exploiting another vulnerability.

### Step 2: Disabling/Bypassing Secure Boot

The attacker takes advantage of weaknesses in Secure Boot's validation logic (detailed in Microsoft’s advisory). Specifically, CVE-2024-26180 is linked to how older or revoked bootloaders can still be loaded (like we’ve seen previously with BlackLotus). The attacker replaces or modifies boot files that Secure Boot should block, but due to this vulnerability, the system fails to block them effectively.

Example Snippet (PowerShell to replace a Bootloader)

# WARNING: For educational purposes only!
Copy-Item -Path "malicious\bootmgfw.efi" -Destination "C:\EFI\Microsoft\Boot\" -Force
bcdedit /set {bootmgr} path \EFI\Microsoft\Boot\bootmgfw.efi
# This overwrites the original boot file with a malicious one that won’t be blocked due to the vulnerability.

Step 3: Installing a Rootkit or Bootkit

After bypassing Secure Boot, attackers can drop a malicious driver or rootkit before Windows loads or tamper with OS components without being detected.

Proof-of-Concept (PoC)

A simple proof-of-concept would involve overwriting a protected EFI binary with a malicious payload and rebooting the device. An attacker could use tools like UEFItool or scripted PowerShell for automation.

# Assume we have admin rights and are booted into WinPE or Recovery Environment
copy my-malicious-bootx64.efi X:\EFI\Boot\bootx64.efi /y

On the next reboot, the malicious code runs before Windows starts, even though Secure Boot should have blocked it.

Attacker installs stealthy and persistent malware

- Antivirus/EDR cannot see or remove the bootkit

How to Protect Yourself

1. Patch ASAP:
Microsoft released updates and new Secure Boot blocklists in March 2024. Apply all Windows Updates immediately.

2. Use TPM and BitLocker:
Enabling BitLocker with TPM makes it much harder to modify boot files.

3. Audit and Monitor:
Monitor for changes in boot configuration using tools like Sysmon or Windows Event Logs.

4. Firmware Updates:
Check your device vendor for UEFI firmware updates regularly.

Links and References

- CVE-2024-26180 — Microsoft Security Advisory
- Windows Secure Boot Explained (Microsoft Docs)
- Kaspersky | BlackLotus Secure Boot Bypass
- UEFITool

Final Thoughts

CVE-2024-26180 is yet another reminder how attackers target the very foundation of computer security: the boot process. Organizations and users must keep Secure Boot protections, firmware, and OS up to date. If an attacker has administrator rights, the game might already be lost — but Secure Boot is supposed to be the last line of defense. This vulnerability threatens that line. Stay patched and aware.

If you want to check your Secure Boot or have questions, don’t hesitate to drop them below!

Disclaimer: This post is for educational purposes only. Misusing this information is illegal and unethical. Always follow your local laws and organization's policies.

Timeline

Published on: 04/09/2024 17:15:36 UTC
Last modified on: 04/10/2024 13:24:00 UTC