CVE-2024-56737

What it actually does

Heap-based buffer overflow in GRUB2 fs/hfs.c when parsing crafted superblock data from an HFS filesystem.

Why it matters to the business

Potential code execution during the boot process on affected systems could allow attackers to compromise machines before the operating system loads, increasing risk of persistent malware or ransomware.

How an attack unfolds

An attacker prepares a malicious HFS filesystem containing specially crafted superblock data that triggers the overflow in GRUB2's parsing routine, then delivers it via removable media or a network boot target so GRUB processes the filesystem during startup.

How to fix it

Upgrade GRUB2 to a fixed version beyond 2.12 that resolves the heap overflow in fs/hfs.c. Verify the update is applied across all boot media and test boot integrity after patching.

How to confirm the fix worked

Confirm GRUB2 version is newer than 2.12 and test that parsing of known-malicious HFS test images no longer causes overflow or crashes.

Typical attack path

1. Create HFS filesystem image with malicious superblock
2. Place image on removable media or configure as boot target
3. Cause target system to boot via GRUB and mount/inspect the image
4. Trigger buffer overflow to gain code execution in the bootloader context

How to detect it

Review bootloader logs and boot partition integrity checks for unexpected HFS filesystem access or crashes during GRUB initialization; look for signs of modified boot media.

What your security team should do

• Prioritize patching GRUB2 on all systems that may encounter untrusted HFS media
• Disable HFS filesystem support in GRUB if not required
• Monitor for unexpected boot failures or anomalies after updates