CVE-2025-0690 is a vulnerability identified in the GRUB bootloader related to its handling of keyboard input via the read command. The issue stems from the use of a 32-bit integer to track the length of user input, which is then used to reallocate the line buffer dynamically. When a sufficiently large input line is provided, this length variable can overflow, causing an out-of-bounds write in the heap-based buffer. This memory corruption can lead to the alteration of GRUB's internal critical data structures. Given GRUB's role in the boot process and secure boot enforcement, such corruption could allow attackers to bypass secure boot mechanisms, undermining system integrity from the earliest stage of system startup. The vulnerability requires privileged access (PR:H) and user interaction (UI:R), and the attack vector is physical or local (AV:P). The CVSS 3.1 base score is 6.1, indicating a medium severity level with high impact on confidentiality, integrity, and availability. No public exploits are known at this time, and no patches have been linked yet. The vulnerability was reserved in January 2025 and published in February 2025, with Red Hat as the assigner. The flaw affects GRUB versions identified as '0' in the data, which likely represents a placeholder or early versions. The vulnerability highlights the risks of integer overflow in memory management during input handling in critical boot components.

The exploitation of CVE-2025-0690 could have significant consequences for organizations relying on GRUB as their bootloader, particularly those enforcing secure boot policies. Successful exploitation can corrupt GRUB's internal data, potentially allowing attackers to bypass secure boot protections, which are designed to prevent unauthorized code execution during system startup. This undermines the trust chain of the boot process, enabling persistent and stealthy malware infections or rootkits that load before the operating system. The impact spans confidentiality, integrity, and availability: confidentiality is at risk if attackers gain early access to system memory or keys; integrity is compromised by tampering with bootloader code or configuration; availability may be affected if the system fails to boot correctly. However, the requirement for privileged access and user interaction limits the attack surface, making remote exploitation unlikely without prior system access. Organizations with high-security requirements, such as government, financial, and critical infrastructure sectors, face elevated risks. The lack of known exploits reduces immediate threat but does not diminish the need for prompt mitigation.

To mitigate CVE-2025-0690, organizations should: 1) Monitor vendor advisories closely and apply patches or updates to GRUB as soon as they become available. 2) Implement strict input validation and bounds checking in GRUB's input handling code to prevent integer overflow and buffer overflows. 3) Restrict physical and local access to systems to prevent unauthorized user interaction that could trigger the vulnerability. 4) Employ secure boot configurations with additional hardware-based protections such as TPM and measured boot to detect unauthorized bootloader modifications. 5) Use system integrity monitoring tools to detect anomalies in bootloader behavior or configuration. 6) Limit the use of privileged accounts and enforce strong authentication to reduce the risk of local exploitation. 7) Conduct regular security audits and penetration testing focusing on boot process security. 8) Consider deploying GRUB alternatives or updated bootloaders if patches are delayed. These measures collectively reduce the likelihood and impact of exploitation beyond generic patching advice.