CVE-2025-1125 is a medium-severity vulnerability affecting the GRUB bootloader's HFS filesystem module. The flaw arises from improper handling of integer overflows when calculating buffer sizes based on user-controlled filesystem metadata parameters. Specifically, when reading data from an HFS filesystem, the module uses metadata values to determine the size of internal buffers. However, it fails to properly check for integer overflow conditions during these calculations. This can cause the grub_malloc() function to allocate a buffer smaller than intended. Subsequently, the hfsplus_open_compressed_real() function writes data beyond the allocated buffer boundary, resulting in an out-of-bounds write. This memory corruption can overwrite critical internal GRUB data structures, potentially allowing an attacker to execute arbitrary code during the boot process. Notably, this exploit can bypass secure boot protections, which are designed to prevent unauthorized code execution at boot time. The vulnerability requires local access to a maliciously crafted HFS filesystem image or partition, and some user interaction is necessary to trigger the flaw (e.g., booting from or mounting the compromised filesystem). The CVSS 3.1 base score is 6.7, reflecting medium severity with high impact on confidentiality, integrity, and availability, but limited by the requirement for local access, higher attack complexity, and user interaction. There are no known exploits in the wild at this time, and no patches or mitigations have been linked yet. This vulnerability primarily impacts systems that use GRUB to boot from or access HFS filesystems, which are commonly associated with Apple devices or dual-boot environments involving macOS volumes. Since GRUB is widely used in Linux and Unix-like systems, especially in multi-boot setups, the vulnerability could affect a range of devices that interact with HFS volumes during boot or runtime.

For European organizations, the impact of CVE-2025-1125 depends on their use of GRUB bootloader and interaction with HFS filesystems. Organizations that maintain dual-boot environments with macOS or use HFS-formatted external drives for data exchange are at risk. Successful exploitation could lead to arbitrary code execution at boot time, allowing attackers to bypass secure boot protections and compromise system integrity before the OS loads. This could facilitate persistent malware infections, unauthorized access to sensitive data, and disruption of critical services. Sectors such as finance, government, research, and critical infrastructure with stringent security requirements could face significant operational and reputational damage if targeted. Additionally, the ability to bypass secure boot undermines hardware-based trust models, increasing the difficulty of detecting and remediating infections. However, since exploitation requires local access and user interaction, remote attacks are less likely, limiting the threat to insiders or attackers with physical or logical access to affected systems. The absence of known exploits in the wild currently reduces immediate risk but does not preclude future weaponization.

1. Avoid mounting or booting from untrusted or unknown HFS filesystem images or devices, especially in environments using GRUB as the bootloader. 2. Implement strict access controls and monitoring for devices and partitions formatted with HFS to prevent unauthorized use. 3. Where possible, disable HFS filesystem support in GRUB if it is not required, reducing the attack surface. 4. Maintain up-to-date backups and recovery plans to restore systems in case of compromise. 5. Monitor for updates from GRUB maintainers and Linux distribution vendors for patches addressing this vulnerability, and apply them promptly once available. 6. Employ endpoint security solutions capable of detecting anomalous bootloader behavior or unauthorized code execution during system startup. 7. Educate users and administrators about the risks of using external HFS volumes and the importance of verifying device integrity before use. 8. For environments requiring HFS support, consider additional integrity verification mechanisms such as cryptographic signatures on boot components to detect tampering.