Overview
CVE-2025-61661 describes a medium severity vulnerability in the GRUB (Grand Unified Bootloader) component. This flaw allows a local attacker to potentially cause a denial-of-service (DoS) condition and possibly data corruption. The vulnerability stems from improper handling of string conversions when GRUB reads information from USB devices.
Technical Details
The vulnerability arises because GRUB mishandles string conversion operations during the boot sequence when interacting with USB devices. Specifically, the bootloader does not adequately validate the length of strings received from USB devices. A malicious USB device, crafted to provide inconsistent length values during string conversion, can exploit this weakness. When GRUB processes this malformed data, it can lead to a crash, resulting in a denial of service.
A local attacker with physical access to the system during the boot process can connect a specially crafted USB device to trigger this vulnerability.
CVSS Analysis
- CVSS Score: 4.8
- Severity: MEDIUM
While the CVSS score indicates a medium severity, it’s important to understand the context. The score reflects the fact that the attacker requires physical access to the system to exploit the vulnerability. However, in scenarios where physical access is easily obtained (e.g., unattended servers, publicly accessible kiosks), the risk is elevated.
Possible Impact
The primary impact of CVE-2025-61661 is a denial of service. A successful exploit will cause GRUB to crash, preventing the system from booting. This can lead to downtime and disruption of services. Although data corruption is a possibility, the exploit’s complexity suggests that the likelihood and extent of data corruption are limited.
The ability to interrupt the boot process can have significant consequences in environments where system availability is critical.
Mitigation and Patch Steps
The most effective mitigation is to apply the patch provided by your operating system vendor or GRUB maintainers. Check your distribution’s security advisories for updates related to CVE-2025-61661.
In the interim, consider the following preventative measures:
- Restrict Physical Access: Limit physical access to systems, especially during the boot process.
- Secure Boot: Implement Secure Boot to prevent unauthorized bootloaders from executing.
- USB Device Monitoring: Implement monitoring and logging of USB device connections to detect suspicious activity.
Stay tuned for official patches from your distribution’s maintainers and apply them promptly.
