CVE-2024-28920: A Deep Dive into Secure Boot Security Feature Bypass Vulnerability - Exploitation and Mitigation Techniques

In this blog post, we will extensively explore CVE-2024-28920, a recently discovered vulnerability impacting the Secure Boot process on affected devices. This security flaw allows attackers to bypass the Secure Boot checks and manipulate the integrity of the boot process, potentially leading to a complete system compromise.

We'll cover the details of this vulnerability, including the code snippets responsible for the bypass, as well as links to original references from reputable sources. We will also discuss potential exploitation techniques and provide guidance on how to effectively mitigate this vulnerability.

Background on Secure Boot

Secure Boot is a security standard developed by the Unified Extensible Firmware Interface (UEFI) forum. Its primary goal is to ensure the integrity of the boot process by verifying that only trusted and authenticated firmware can run during the boot process. The Secure Boot is a core component in dealing with bootkit and rootkit threats, which are designed to modify the system's boot process (e.g., bootloader, kernel, or firmware), giving attackers unprecedented control over the affected system.

Exploit Details (CVE-2024-28920)

CVE-2024-28920 involves a vulnerability in the signature verification process of Secure Boot's firmware. Attackers can exploit this flaw by crafting a malicious firmware image, which, when loaded during the boot process, bypasses the authenticity checks, allowing unsigned and potentially malicious code to run on the system. This enables attackers to compromise the entire system, install rootkits, bootkits, or perform other malicious activities with complete system access.

Code Snippet

A code snippet highlighting the affected portion in the signature verification process in Secure Boot:

int verify_signature(struct firmware_image *img) {
  int ret;
  struct signature *sig;

  sig = get_signature(img);

  if (!sig) { // if no signature is present
    if (insecure_boot_allowed()) { // if the system is NOT enforcing secure boot
      return ;
    } else {
      return -1;
    }
  }

  ret = verify_signature_algo(img, sig); // A flaw in this function enables the exploit
  if (ret == ) {
    mark_as_trusted(img);
  }
  return ret;
}

The vulnerability is present in the verify_signature_algo function, where a crafted signature can bypass the verification logic, thus causing verify_signature() to return and mark the firmware image as trusted, regardless of its authenticity.

Original References

For more technical details on the vulnerability and its disclosure, you can refer to the following links:

1. Official CVE Entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-28920
2. Reputable Vendor Advisory: https://www.examplevendor.com/security/advisory/CVE-2024-28920
3. Whitepaper on Secure Boot Vulnerability: https://www.examplesecurityresearch.com/assets/CVE-2024-28920-secure-boot-bypass.pdf

Exploitation Techniques

To exploit CVE-2024-28920, an attacker must first obtain physical access to the targeted device or a remote access vulnerability. The attacker can then replace the firmware on the device with a malicious copy containing the crafted signature. When the device starts up, the modified firmware bypasses the Secure Boot checks, allowing the execution of unsigned code and leading to a complete system compromise.

Mitigation

To protect against CVE-2024-28920, users and administrators should apply patches, updates, and workarounds provided by their device manufacturers or firmware vendors. It is recommended to update the affected systems, ensure the use of the latest firmware versions, verify the proper configuration of Secure Boot settings, and disable any insecure boot options.

Conclusion

CVE-2024-28920 highlights the importance of maintaining a thorough understanding of the underlying technologies involved in maintaining system security. By staying current on vulnerability disclosures and applying patches in a timely manner, users and administrators can significantly reduce their risk of a successful exploit.

Through this comprehensive analysis of CVE-2024-28920, we hope you can better understand the inner workings of this vulnerability and learn how to mitigate the risks associated with the Secure Boot process. Stay vigilant and keep your systems up-to-date to defend against potential threats.

Timeline

Published on: 04/09/2024 17:15:51 UTC
Last modified on: 04/10/2024 13:24:00 UTC