CVE-2025-0690 is a vulnerability in the GRUB bootloader related to an out-of-bounds write caused by an integer overflow during keyboard input processing. Specifically, the read command reads user keyboard input and tracks the input length using a 32-bit integer. When a line input is sufficiently large, this length value can overflow, causing the subsequent buffer reallocation to be miscalculated. This leads to a heap-based buffer overflow where data can be written beyond the allocated memory bounds. Such memory corruption can alter GRUB's internal critical data structures, potentially allowing an attacker to bypass secure boot protections. Secure boot is a critical security feature that ensures only trusted software is loaded during system startup, so bypassing it can enable persistent and stealthy compromise of the system. Exploitation requires local privileged access (PR:H), user interaction (UI:R), and physical or remote local access (AV:P). The CVSS v3.1 score is 6.1, reflecting medium severity due to the combination of high impact on confidentiality, integrity, and availability but limited attack vector and prerequisites. No known exploits are currently reported in the wild. The vulnerability affects GRUB versions identified as '0' in the data, which likely refers to a specific or default version placeholder, indicating the need for further vendor clarification. The flaw was reserved in January 2025 and published in February 2025, with enrichment from CISA and Red Hat assigner details. No patches or mitigations are linked yet, emphasizing the need for vendor response and user vigilance.

The primary impact of CVE-2025-0690 is the potential compromise of the secure boot process, which is foundational for system trust and integrity. Successful exploitation can allow attackers to execute arbitrary code early in the boot sequence, bypassing firmware and OS-level security controls. This can lead to persistent malware infections, rootkits, or unauthorized system modifications that are difficult to detect and remediate. For European organizations, particularly those in critical infrastructure, government, finance, and healthcare sectors, this vulnerability poses a significant risk to system integrity and confidentiality. The ability to bypass secure boot undermines hardware-based security assurances and can facilitate advanced persistent threats (APTs). Additionally, the vulnerability affects availability by potentially causing system crashes or boot failures due to heap corruption. Since exploitation requires local privileged access and user interaction, the threat is more relevant in environments where attackers can gain such access, including insider threats or compromised administrative accounts. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the need for proactive mitigation.

1. Monitor vendor advisories closely for official patches or updates to GRUB addressing CVE-2025-0690 and apply them promptly. 2. Restrict local privileged access to trusted personnel only, enforcing strict access controls and multi-factor authentication to reduce the risk of exploitation. 3. Implement input validation and limit input sizes where possible in environments that interact with GRUB or its configuration to prevent triggering the integer overflow. 4. Employ secure boot verification and attestation mechanisms to detect unauthorized changes to boot components. 5. Use system integrity monitoring tools to detect anomalies in bootloader behavior or configuration. 6. Conduct regular audits of privileged accounts and monitor for suspicious user activity that could indicate attempts to exploit this vulnerability. 7. In high-security environments, consider hardware-based root of trust solutions and firmware protections that complement secure boot. 8. Educate system administrators about the risks of local privilege escalation vulnerabilities and the importance of minimizing user interaction with low-level boot components. 9. Prepare incident response plans that include boot-level compromise scenarios to enable rapid containment and recovery.