CVE-2025-61661 is a vulnerability identified in the GRUB bootloader component of Red Hat Enterprise Linux 10. The flaw stems from an incorrect calculation of buffer size during string conversion when GRUB reads information from USB devices during the boot sequence. Specifically, the bootloader mishandles length values, leading to inconsistent buffer allocation. An attacker with local physical access can exploit this by connecting a specially crafted USB device during system startup. This triggers the vulnerability, causing GRUB to crash, which results in a denial of service condition. Although data corruption is possible due to the nature of the buffer miscalculation, the exploit complexity and conditions make this less likely. The vulnerability does not require any privileges or user interaction but does require physical presence and timing during boot. The CVSS 3.1 base score is 4.8, reflecting medium severity, with attack vector as physical, high attack complexity, no privileges required, no user interaction, no confidentiality impact, low integrity impact, and high availability impact. No known exploits have been reported in the wild, and no patches have been linked yet. This vulnerability highlights risks in the boot process where hardware input is trusted without sufficient validation.

For European organizations, the primary impact is denial of service at system boot, potentially causing downtime and operational disruption. This can be particularly critical for servers and infrastructure systems relying on Red Hat Enterprise Linux 10, especially in environments where physical access controls are less stringent, such as shared office spaces or data centers with multiple tenants. Although data corruption is possible, it is unlikely to be widespread due to exploit complexity. The vulnerability could be leveraged by insiders or attackers with physical access to disrupt services, impacting availability of critical systems. Sectors such as finance, healthcare, government, and industrial control systems that rely on Red Hat Enterprise Linux 10 for critical operations could face operational risks. The requirement for physical access limits remote exploitation but does not eliminate risk in environments with insufficient physical security. The lack of known exploits reduces immediate threat but patching and mitigation remain important to prevent future exploitation.

1. Restrict physical access to critical systems running Red Hat Enterprise Linux 10, especially during boot sequences. 2. Disable USB boot options in BIOS/UEFI settings where possible to prevent booting from unauthorized USB devices. 3. Implement strong physical security controls in data centers and office environments to prevent unauthorized device connections. 4. Monitor and audit boot device configurations to detect unauthorized changes. 5. Once patches or updates are released by Red Hat, apply them promptly to address the vulnerability. 6. Consider using secure boot mechanisms and hardware root of trust features to validate bootloader integrity. 7. Educate system administrators about the risks of physical attacks during boot and enforce strict device connection policies. 8. Use endpoint security solutions that can detect and alert on unauthorized USB device connections. These steps go beyond generic advice by focusing on physical security, boot configuration hardening, and proactive monitoring specific to this vulnerability.