CVE-2025-54771 is a use-after-free vulnerability identified in GNU GRUB2, the widely used bootloader responsible for loading operating systems on many Linux-based systems. The flaw arises during the file-closing process within GRUB2, where a memory pointer referencing a file system structure is incorrectly retained after the file is closed. This expired pointer leads to a use-after-free condition, which can be exploited by an attacker to cause the GRUB2 process to crash. The primary consequence of this vulnerability is a denial of service (DoS) condition, as the bootloader crash prevents the system from booting properly. Although the vulnerability mainly impacts availability, the description does not exclude the possibility of data integrity or confidentiality compromise, though such impacts are less likely. The vulnerability has a CVSS 3.1 base score of 4.9, indicating medium severity. The attack vector is local (AV:L), requiring the attacker to have local access to the system, with high attack complexity (AC:H), no privileges required (PR:N), and no user interaction (UI:N). No known exploits are currently reported in the wild, and no patches have been linked yet. Given GRUB2's critical role in system startup, exploitation could disrupt operations until recovery actions are taken. The vulnerability affects all versions of GRUB2 as indicated, though specific version details are not provided. The flaw was reserved in July 2025 and published in November 2025.

For European organizations, the impact of CVE-2025-54771 primarily manifests as a denial of service, potentially causing system downtime due to boot failures. This can disrupt critical services, especially in sectors relying heavily on Linux-based infrastructure such as finance, telecommunications, government, and energy. Although the vulnerability requires local access and has high attack complexity, insider threats or attackers with physical or remote local access could exploit it to cause outages. The potential, albeit less likely, risk to data confidentiality or integrity could have regulatory implications under GDPR if sensitive data is involved. Systems running GRUB2 without mitigation are vulnerable to boot interruptions, which could delay incident response and recovery. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits post-disclosure. Organizations with automated or remote boot management may face additional challenges in recovery. Overall, the impact is medium but could escalate in environments where availability is critical.

1. Monitor official GNU and Linux distribution security advisories closely for patches addressing CVE-2025-54771 and apply them promptly once available. 2. Implement secure boot mechanisms and bootloader integrity verification to detect and prevent unauthorized modifications or exploitation attempts. 3. Restrict local access to critical systems by enforcing strict physical security controls and limiting administrative privileges to reduce the attack surface. 4. Employ system hardening practices including disabling unnecessary local accounts and services that could be leveraged for local exploitation. 5. Maintain comprehensive backup and recovery procedures to restore systems quickly in case of boot failures caused by exploitation. 6. Use intrusion detection systems capable of monitoring boot process anomalies and local privilege escalations. 7. For environments using remote management, ensure out-of-band management consoles are secured and monitored to prevent unauthorized local access. 8. Conduct regular security training to raise awareness about local threat vectors and insider risks. 9. Consider deploying kernel lockdown features or bootloader alternatives if feasible to reduce dependency on vulnerable GRUB2 versions until patches are applied.