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 during buffer size calculations when reading metadata from HFS filesystems. Specifically, the module uses user-controlled parameters from the filesystem metadata to compute internal buffer sizes without adequate overflow checks. This can cause an integer overflow, leading to a grub_malloc() call that allocates a smaller buffer than intended. Subsequently, the function hfsplus_open_compressed_real() 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 within the bootloader context. Notably, this exploit can bypass secure boot protections, which are designed to prevent unauthorized code execution during system startup. The vulnerability requires local access (attack vector: local), high attack complexity, and high privileges, with no user interaction needed. The CVSS v3.1 base score is 6.4, reflecting significant confidentiality, integrity, and availability impacts if exploited. Although no known exploits are currently reported in the wild, the flaw poses a serious risk to systems using GRUB with HFS filesystem support, especially in environments where maliciously crafted HFS volumes could be introduced.

For European organizations, the impact of CVE-2025-1125 can be substantial, particularly for enterprises and government entities relying on GRUB as their bootloader on systems that may mount or interact with HFS filesystems. Successful exploitation could lead to arbitrary code execution at boot time, undermining system integrity and bypassing secure boot mechanisms. This could facilitate persistent malware infections, unauthorized system control, or disruption of critical services. Confidential data could be exposed or altered, and system availability compromised. Organizations in sectors such as finance, healthcare, critical infrastructure, and government are especially at risk due to the potential for targeted attacks leveraging this vulnerability. The requirement for local privileged access somewhat limits remote exploitation, but insider threats or scenarios involving compromised local accounts remain concerning. Additionally, environments using dual-boot or multi-OS setups with macOS or legacy HFS volumes may be more exposed.

To mitigate CVE-2025-1125, organizations should: 1) Apply vendor patches or updates to GRUB as soon as they become available, ensuring the integer overflow checks are properly implemented. 2) Restrict local administrative access to trusted personnel only, minimizing the risk of malicious local actors introducing crafted HFS filesystems. 3) Audit and monitor systems for unusual bootloader behavior or unauthorized modifications to boot components. 4) Avoid mounting or interacting with untrusted HFS filesystems, especially from external or removable media. 5) Implement strict endpoint security controls and integrity verification mechanisms for bootloader components. 6) For environments requiring secure boot, verify that bootloader updates maintain compatibility with secure boot policies and consider additional hardware-based root of trust protections. 7) Conduct regular security training to raise awareness about the risks of local privilege misuse and filesystem-based attacks.