CVE-2025-0677 is a vulnerability identified in the GRUB2 bootloader, specifically within its Unix File System (UFS) module. The flaw arises during the symlink lookup process where GRUB2 checks the inode's data size to allocate an internal buffer for reading file content. However, it fails to verify if the symlink data size has overflowed, resulting in grub_malloc() being called with a buffer size smaller than necessary. Consequently, when grub_ufs_lookup_symlink() reads data from disk into this buffer, it writes beyond the allocated memory boundary, causing an out-of-bounds write on the heap. This heap corruption can be exploited by an attacker who crafts a malicious filesystem, potentially enabling arbitrary code execution within the bootloader context. Such code execution can be used to bypass secure boot mechanisms, undermining the system's trusted boot chain. The vulnerability requires local access with high privileges (as indicated by the CVSS vector AV:L/PR:H) and does not require user interaction. The attack complexity is high due to the need to craft a malicious filesystem and gain local access. The flaw affects the confidentiality, integrity, and availability of the system by allowing unauthorized code execution at a critical boot stage. No patches or known exploits are currently reported, but the vulnerability is publicly disclosed and assigned a CVSS score of 6.4, reflecting medium severity.

For European organizations, this vulnerability poses a significant risk to systems using GRUB2 with UFS support, particularly in environments where secure boot is critical, such as government, finance, healthcare, and critical infrastructure sectors. Exploitation could allow attackers to bypass secure boot protections, leading to persistent malware infections that survive OS reinstalls or firmware updates. This undermines system integrity and confidentiality, potentially exposing sensitive data or enabling further lateral movement within networks. The requirement for local high-privilege access limits remote exploitation but does not eliminate risk, especially in environments with shared access or compromised insider threats. The impact extends to availability if heap corruption causes boot failures or system instability. Given the foundational role of GRUB2 in system startup, successful exploitation could disrupt operations and complicate incident response. European organizations with legacy systems or custom UFS filesystems may be particularly vulnerable. The absence of known exploits provides a window for proactive mitigation, but the medium severity rating warrants timely attention.

Organizations should monitor for official patches or updates from GRUB2 maintainers and apply them promptly once available. In the interim, restrict local administrative access to trusted personnel only and enforce strict access controls to prevent unauthorized local logins. Audit systems for the use of UFS filesystems with GRUB2 and consider migrating to more commonly used and actively maintained filesystems if feasible. Employ integrity verification mechanisms for boot components, such as TPM-based measurements and secure boot policies, to detect unauthorized modifications. Regularly review and harden bootloader configurations to minimize attack surface. Implement comprehensive endpoint security solutions that can detect anomalous behavior indicative of boot-level compromise. For environments requiring high assurance, consider hardware-based root of trust solutions that complement secure boot. Finally, maintain robust incident response plans that include boot-level compromise scenarios.