CVE-2025-0690 is a medium severity vulnerability involving an out-of-bounds write in the GRUB bootloader's handling of keyboard input. Specifically, the vulnerability arises from the 'read' command used to capture user keyboard input, where the input length is stored in a 32-bit integer. When processing a sufficiently large input line, this integer can overflow, causing the program to incorrectly reallocate the line buffer size. This leads to a heap-based buffer overflow, allowing an attacker to overwrite critical internal data structures within GRUB. Given GRUB's role as a bootloader responsible for initializing the operating system, corruption of its internal data could enable an attacker to bypass Secure Boot protections. This bypass could allow unauthorized code execution early in the boot process, undermining system integrity and trust. The vulnerability requires local privileges (PR:H) and user interaction (UI:R) to exploit, with low attack complexity (AC:L) but remote attack vector limited to physical or local access (AV:P). The CVSS 3.1 score is 6.1, reflecting the significant impact on confidentiality, integrity, and availability if exploited. No known exploits are currently in the wild, and no patches or vendor-specific product details are provided yet. However, the potential to compromise Secure Boot makes this a critical concern for systems relying on GRUB for secure bootstrapping, especially in environments where physical or local access is possible.

For European organizations, the impact of CVE-2025-0690 could be substantial, particularly for enterprises and government agencies that rely on Secure Boot to ensure platform integrity and prevent unauthorized firmware or OS loaders. Successful exploitation could allow attackers with local access to bypass Secure Boot protections, leading to persistent malware infections, rootkits, or firmware-level compromises that are difficult to detect and remediate. This could result in data breaches, disruption of critical services, and loss of trust in IT infrastructure. Organizations in sectors such as finance, healthcare, critical infrastructure, and government are especially at risk due to the sensitivity of their data and the regulatory requirements around system integrity and security. Moreover, the requirement for local access and user interaction means insider threats or attackers with physical access to devices pose the greatest risk. The vulnerability also raises concerns for endpoint security in hybrid work environments where devices may be physically accessible outside secure premises.

To mitigate CVE-2025-0690, organizations should: 1) Monitor for vendor advisories and apply patches or updates to GRUB as soon as they become available. 2) Implement strict physical security controls to limit unauthorized local access to devices, including secure storage and access logging. 3) Enforce strong user authentication and restrict user privileges to minimize the risk of malicious input or exploitation by insiders. 4) Employ hardware-based security features such as TPM and measured boot to complement Secure Boot and detect boot-time tampering. 5) Conduct regular integrity checks of bootloader and firmware components using trusted tools. 6) Educate users and administrators about the risks of local exploitation and the importance of reporting suspicious activity. 7) Consider deploying endpoint detection and response (EDR) solutions capable of detecting anomalous bootloader behavior or unauthorized changes to boot configurations. These measures go beyond generic patching advice by emphasizing layered security controls around physical access, privilege management, and boot integrity verification.