GRUB2, Heap-based Buffer Overflow, CVE-2025-0678 (Critical)

How the CVE Works:

CVE-2025-0678 is a critical vulnerability in GRUB2, specifically within its squash4 filesystem module. When GRUB2 reads data from a squash4 filesystem, it uses user-controlled parameters from the filesystem geometry to determine the internal buffer size. However, the module fails to properly validate these parameters for integer overflows. This flaw allows an attacker to craft a malicious squash4 filesystem that triggers an overflow during buffer size calculations. As a result, `grub_malloc()` allocates a smaller buffer than required, leading to a heap-based out-of-bounds write during the `direct_read()` operation. This can corrupt GRUB2’s internal data structures, potentially enabling arbitrary code execution and bypassing secure boot protections.

DailyCVE Form:

Platform: GRUB2
Version: All versions with squash4 module
Vulnerability: Heap-based Buffer Overflow
Severity: Critical
Date: 03/03/2025

What Undercode Say:

Exploitation:

1. Craft Malicious Filesystem: Create a squash4 filesystem with manipulated geometry parameters to trigger the integer overflow.
2. Trigger Overflow: Load the malicious filesystem during GRUB2 initialization.
3. Out-of-Bounds Write: Exploit the heap corruption to overwrite critical GRUB2 data structures.
4. Arbitrary Code Execution: Use the corrupted data to execute malicious code, bypassing secure boot.

Protection:

1. Patch GRUB2: Apply the latest security patches from your distribution.
2. Disable squash4: If unused, disable the squash4 module in GRUB2 configuration.
3. Secure Boot: Ensure secure boot is enabled to mitigate potential exploitation.
4. Input Validation: Implement additional checks for filesystem geometry parameters.

Commands:

• Check GRUB2 version:

`grub-install –version`

• Disable squash4 module:

Edit `/etc/default/grub` and add `GRUB_DISABLE_MODULES=”squash4″`

• Update GRUB2:

`sudo apt update && sudo apt upgrade grub2`

Code Snippets:

• Patch Example:

  if (size > MAX_BUFFER_SIZE || size < 0) {
  return GRUB_ERR_BAD_FS;
  }
  

• Exploit PoC:

  import struct
  with open("malicious.squash4", "wb") as f:
  f.write(struct.pack("<I", 0xFFFFFFFF)) Trigger overflow
  

• Mitigation Script:

  !/bin/bash
  if grep -q "squash4" /boot/grub/grub.cfg; then
  echo "squash4 module detected. Disabling..."
  sudo sed -i 's/GRUB_DISABLE_MODULES=""/GRUB_DISABLE_MODULES="squash4"/' /etc/default/grub
  sudo update-grub
  fi
  

  Analytics:

• CVSS 4.0 Score: 9.8 (Critical)
• Attack Vector: Local
• Impact: Code Execution, Secure Boot Bypass
• Affected Systems: Systems using GRUB2 with squash4 module
• Patch Availability: Yes (Check vendor updates)
  By understanding and mitigating CVE-2025-0678, users can protect their systems from potential exploitation and ensure secure boot integrity.

  References:

  Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-0678
  Extra Source Hub:
  Undercode

Join Our Cyber World:

Whatsapp
Telegram