CVE-2025-0684: Critical Flaw Found in grub2 Potentially Leading to Arbitrary Code Execution and Bypassing Secure Boot Protections

A significant security vulnerability (CVE-2025-0684) has been discovered in the grub2 bootloader, which is commonly used in many Linux-based systems. The vulnerability lies in the way grub2 performs symlink lookup operations on a reiserfs filesystem and it improperly checks for integer overflows.

This flaw affects grub's reiserfs filesystem module, which utilizes user-controlled parameters to determine the internal buffer size. However, the module does not properly verify if an integer overflow has occurred during the calculation of the buffer size.

A maliciously crafted filesystem could cause some of these buffer size calculations to overflow, resulting in the execution of a grub_malloc() operation with a smaller size than expected. As a consequence, the grub_reiserfs_read_symlink() function will call grub_reiserfs_read_real() with an overflown length parameter, triggering a heap-based out-of-bounds write during data reading.

This vulnerability could be exploited maliciously to corrupt grub's critical internal data, potentially leading to arbitrary code execution. This could allow attackers to bypass secure boot protections, which are essential for maintaining system security and preventing unauthorized access.

Here is a code snippet demonstrating the issue

// Insufficient validation on buffer size
int grub_reiserfs_read_symlink (grub_file_t file, char *symlink)
{
  // ...
  unsigned int buf_size;
  grub_uint8_t *buf;
  // ...
  buf_size = reiserfs_get_block_size (&data->sblock) * N_LEAF_NODES;
  buf = grub_malloc (buf_size);
  if (!buf)
    return -1;
  
  // Grub_reiserfs_read_real is called with a potentially overflowed buf_size
  err = grub_reiserfs_read_real (file->fs->dev,
                                 GET_HASH_KEY (&key),
                                 buf, buf_size, &key);
  // ...
}

The original reference detailing the vulnerability can be found in this source.

As this issue poses a significant risk to systems and their security protections, users and administrators are urged to update to the latest available grub2 version which incorporates relevant patches addressing this vulnerability. Further information on how to apply these updates can be found in your system's documentation or by consulting experienced professionals.

Exploit details for CVE-2025-0684

Due to the nature of this vulnerability, it mainly targets systems that use the reiserfs filesystem, hence the scope of potential targets is limited. Successful exploitation can enable an attacker with local access to control the execution flow of the bootloader, potentially bypassing secure boot protections and executing malicious code with elevated privileges.

In conclusion, this vulnerability (CVE-2025-0684) in grub2 should be addressed immediately to prevent potential exposure to arbitrary code execution and bypassing secure boot protections. Users and administrators should apply the appropriate updates as soon as possible to ensure the proper functioning and security of their systems.

Timeline

Published on: 03/03/2025 18:15:30 UTC