CVE-2024-56737: Exploring a Heap-Based Buffer Overflow Vulnerability in GNU GRUB (GRUB2) Through 2.12 with Crafted SBlock Data in an HFS Filesystem

In this long-read post, we will delve into an interesting heap-based buffer overflow vulnerability, known as CVE-2024-56737, that affects GNU GRUB (also known as GRUB2) through version 2.12. This critical vulnerability exists due to improperly handling crafted sblock data in an HFS filesystem, which could potentially allow a malicious attacker to exploit the bootloader, resulting in severe damage to the targeted system.

We will look at the affected code snippets, links to original references, and exploit details for a better understanding of the vulnerability and how it can be mitigated.

Background

GNU GRUB, or simply GRUB, is a popular open-source, multiboot-capable bootloader originally developed for UNIX-like systems such as Linux. It is designed to function with various operating systems installed on the same machine by providing a user-friendly boot menu for selection.

However, the GRUB2 implementation, specifically in versions up to 2.12, has been found to contain a critical vulnerability in its fs/hfs.c code segment that makes the system susceptible to heap-based buffer overflow attacks.

Exploit Details

The vulnerability lies within the handling of crafted sblock data in the HFS filesystem implementation in the fs/hfs.c file of GNU GRUB. This could potentially lead to a heap-based buffer overflow, allowing malicious attackers to execute arbitrary code, crash systems, or even brick devices.

Below is a code snippet of the vulnerable function found in the fs/hfs.c file

static grub_err_t
grub_hfs_mount (struct grub_hfs_data *data)
{
...
  /* Read the volume header.  */
  if (grub_disk_read (data->disk, 2, , sizeof (struct grub_hfs_sblock),
			  &data->sblock))
    return grub_error (GRUB_ERR_BAD_FS, "not an HFS filesystem");
...
 }

The vulnerability arises due to the lack of proper input validation when processing the sblock data when mounting an HFS filesystem.

According to the analysis, if an attacker carefully crafts the sblock data, they could potentially cause a buffer overflow, leading to arbitrary code execution, denial of service (DoS), or system crashes.

The original references for CVE-2024-56737 can be found here

1. CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-56737
2. NVD - National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2024-56737

Mitigation and Conclusion

To address this vulnerability, it is essential to apply the appropriate security patches or upgrade to a newer, fixed version of GNU GRUB. It is also advised to restrict access to the bootloader and ensure strict validation of input data. Regularly updating and auditing the codebase for potential vulnerabilities is another preventive measure that can be employed.

In conclusion, CVE-2024-56737 is a critical heap-based buffer overflow vulnerability affecting GNU GRUB2 through version 2.12. If successfully exploited, it could lead to severe consequences, including arbitrary code execution, system crashes, and potentially bricking devices. To mitigate this risk, it is crucial to apply security patches, upgrade to the fixed version, and follow best security practices to minimize the risk of exploitation.

Timeline

Published on: 12/29/2024 07:15:06 UTC
Last modified on: 12/31/2024 19:15:48 UTC