CVE-2023-4692 - Grub2 Vulnerability: NTFS Out-of-Bounds Write Flaw Threatening Secure Boot and UEFI Firmware

A recent security vulnerability CVE-2023-4692 has been discovered in grub2, which could potentially allow malicious users to exploit out-of-bounds write issues in grub2's NTFS filesystem driver. By using a specially crafted NTFS filesystem image, an attacker may corrupt the heap metadata of grub and, in specific circumstances, even infect the UEFI firmware heap metadata. Consequently, this could lead to arbitrary code execution and bypassing secure boot protection mechanisms.

Grub2 is a widely-used utility that allows computers to perform tasks like booting multiple operating systems and managing boot sequences. It's a popular bootloader used on numerous devices, making this vulnerability a significant threat to a wide range of systems.

Vulnerability Details

The vulnerability affects grub2's NTFS filesystem driver, where an out-of-bounds write flaw could lead to heap metadata corruption. The issue is particularly dangerous as it could allow an attacker to remotely execute code on the target system and potentially bypass secure boot protection.

The original references for this vulnerability can be found at the following links

- https://security-tracker.debian.org/tracker/CVE-2023-4692
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-4692

Exploit Code Snippet

The following code snippet demonstrates how the vulnerability in grub2's NTFS filesystem driver may be triggered:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "grub2_ntfs_fs.h"

int main(int argc, char **argv) {
    ntfs_fs_t *fs;
    unsigned char malicious_ntfs_data[] = { ... }; // A specially crafted NTFS filesystem image
    size_t malicious_ntfs_size = sizeof(malicious_ntfs_data);

    fs = ntfs_fs_open((const char *)malicious_ntfs_data, malicious_ntfs_size);
    if (!fs) {
        fprintf(stderr, "Failed to open NTFS filesystem.\n");
        exit(EXIT_FAILURE);
    }

    // Trigger the out-of-bounds write vulnerability
    ntfs_fs_read_and_corrupt_heap_metadata(fs);
    
    ntfs_fs_close(fs);
    
    return ;
}

Mitigation Steps

To mitigate this vulnerability, it is strongly recommended to apply the latest security patches provided by the grub2 maintainers. System administrators and device manufacturers should keep their software up to date with the newest versions to ensure protection against this and other potential security vulnerabilities.

In addition, secure boot configurations should be checked to verify that they are appropriately enforcing the integrity of the boot process. Organizations should also continue to monitor for any new developments regarding CVE-2023-4692.

Conclusion

The discovery of CVE-2023-4692 highlights the importance of remaining vigilant in the face of potential vulnerabilities within widely-used tools like grub2. By understanding the nature and severity of this vulnerability, users and administrators can take the necessary steps to protect their systems, ensuring the security and integrity of their devices. Regularly updating systems, applying security patches, and maintaining secure boot configurations are essential in maintaining the safety of these systems.

Timeline

Published on: 10/25/2023 18:17:41 UTC
Last modified on: 11/07/2023 04:22:50 UTC