CVE-2025-61664 is a Use After Free vulnerability discovered in the GNU GRUB2 bootloader, specifically within its normal module. The root cause is the improper unregistration of the normal_exit command when the associated module is unloaded. This leads to a scenario where the system can invoke the normal_exit command after the module has been removed, causing the bootloader to access memory that has already been freed. Such expired pointer dereference can result in system instability, including crashes (denial of service), and may also allow attackers to impact data confidentiality and integrity by manipulating memory contents. The vulnerability has a CVSS 3.1 base score of 4.9, indicating medium severity, with an attack vector limited to local access (AV:L), high attack complexity (AC:H), no privileges required (PR:N), and no user interaction (UI:N). The scope is unchanged (S:U), with low impacts on confidentiality, integrity, and availability (C:L/I:L/A:L). No known exploits are currently reported in the wild. GRUB2 is a critical component in the boot process of many Linux distributions and Unix-like operating systems, making this vulnerability significant for systems relying on it. The vulnerability was reserved in late September 2025 and published in November 2025. No patches or exploit indicators are currently available, highlighting the need for vigilance and prompt patching once fixes are released.

The primary impact of CVE-2025-61664 is the potential for denial of service through system crashes caused by dereferencing freed memory in the bootloader. This can disrupt system availability, particularly during boot, potentially leading to downtime and operational interruptions. Additionally, the vulnerability may allow attackers to affect data confidentiality and integrity by manipulating memory contents during the boot process, although this impact is assessed as low. Since GRUB2 is used extensively across Linux servers, desktops, and embedded systems, the vulnerability poses a risk to a broad range of organizations globally. Attackers with local access could exploit this flaw to destabilize systems or potentially gain further footholds if combined with other vulnerabilities. The requirement for local access and high attack complexity limits the ease of exploitation, reducing immediate widespread risk. However, the critical nature of the bootloader means successful exploitation could have severe consequences for system recovery and trust in system integrity.

Organizations should prioritize monitoring vendor advisories for patches addressing CVE-2025-61664 and apply updates promptly once available. Until patches are released, restrict local access to trusted users and administrators only, minimizing the risk of exploitation. Implement bootloader integrity verification mechanisms such as Secure Boot to detect unauthorized modifications or abnormal behavior during the boot process. Regularly audit and harden system boot configurations to reduce attack surface. Employ system monitoring to detect unusual boot failures or crashes that could indicate exploitation attempts. Consider using kernel lockdown features and access control policies to limit the ability to unload or manipulate bootloader modules. In environments where physical access is possible, ensure physical security controls to prevent unauthorized local access. Finally, maintain comprehensive backups and recovery plans to mitigate the impact of potential system crashes caused by exploitation.