CVE-2025-61661

A vulnerability has been identified in the GRUB (Grand Unified Bootloader) component. This flaw occurs because the bootloader mishandles string conversion when reading information from a USB device, allowing an attacker to exploit inconsistent length values. A local attacker can connect a maliciously configured USB device during the boot sequence to trigger this issue. A successful exploitation may lead GRUB to crash, leading to a Denial of Service. Data corruption may be also possible, although given the complexity of the exploit the impact is most likely limited.

This vulnerability was rated as having the impact of Moderate by the Red Hat Product Security Engineering team. To exploit this flaw the attacker needs to have physical access to the machine and connect a maliciously crafted USB device which will leverage the lack of string size validation to cause a out-of-bounds write when reading strings from it. Even though the existence of a possible out-of-bounds write, given the complexity of producing the exploit, the impact is most likely limited to leading grub to crash causing a Denial-of-Service kind of attack or uncontrolled data corruption which presents a Low impact in the Integrity point of the CIA triad in the CVSS scoring.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

As a mitigation Red Hat doesn't recommend to connect untrusted or unknown USB devices to the machine.