CVE-2025-61661: Grub2: grub2: out-of-bounds write via malicious usb device
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.
Other sources
Grub2: grub2: out-of-bounds write via malicious usb device
— Microsoft
When reading strings from a USB device in grubusbgetstring() function the initial length is taken from first message read. Then this value is used to allocate memory for UTF-8 destination string. However, during conversion the length value is taken from the second USB device read. This can be dangerous if malicious USB devices are connected because they may expose smaller initial length value, used for memory allocation, and subsequent read may provide larger length, used during conversion. Such behavior may lead to heap overflow during UTF-16 to UTF-8 conversion.
— Red Hat
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2025-61661?
The severity of CVE-2025-61661 is considered medium due to the potential for local attackers to exploit string conversion mishandling in the bootloader.
How do I fix CVE-2025-61661?
To fix CVE-2025-61661, update the GRUB bootloader to the latest version that addresses this vulnerability.
Who is affected by CVE-2025-61661?
CVE-2025-61661 affects users of the GNU GRUB bootloader on systems that utilize this software for managing boot processes.
What are the potential impacts of CVE-2025-61661?
The potential impacts of CVE-2025-61661 include unauthorized access or privilege escalation due to inconsistent string length handling.
Is CVE-2025-61661 a remote or local vulnerability?
CVE-2025-61661 is classified as a local vulnerability, requiring access to the affected system for exploitation.