CVE-2026-97876
MediumCVSS 6.4Exploitation Probability (EPSS)
Low risk1th percentile - higher than 1% of all known CVEs
Summary
A local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command, allowing an attacker to write data at an attacker-controlled address and disable module verification.
Risk Assessment
An attacker with local access can load unsigned kernel modules, bypassing Secure Boot and lockdown protections, leading to unauthorized code execution at boot level. The risk is high as it undermines the integrity of the boot trust chain.
Recommendation
Update GRUB to a version containing the MMIO address validation fix. Restrict local access to GRUB configuration and consider additional boot protection measures such as TPM measurement.
Other vulnerabilities in GRUB
See all- CVE-2022-2601High
A buffer overflow was found in grub_font_construct_glyph(). A malicious crafted pf2 font can lead to an overflow when calculating the max_glyph_size value, allocating a smaller than needed buffer for the glyph.
- CVE-2025-61662High
A Use-After-Free vulnerability has been discovered in GRUB's gettext module. The flaw occurs because the gettext command remains registered in memory after its module is unloaded. An attacker can invoke the orphaned command, causing access to an invalid memory location.
- CVE-2025-61661Medium
A vulnerability has been identified in the GRUB (Grand Unified Bootloader) component due to improper string conversion when reading data from a USB device. A local attacker can connect a maliciously configured USB device during boot sequence, causing GRUB to crash and leading to a Denial of Service (DoS). Data corruption may also be possible, but due to exploit complexity the impact is likely limited.
- CVE-2025-4382Medium
In systems using LUKS-encrypted disks with GRUB configured for TPM-based auto-decryption, an attacker with physical access can corrupt the filesystem superblock. This forces GRUB into rescue mode while the decryption key remains in memory, allowing access to unencrypted data without authentication.
- CVE-2024-45782High
A flaw was found in the HFS filesystem driver in GRUB. When mounting an HFS volume, grub_fs_mount() performs a strcpy() on the user-provided volume name without validating its length, leading to a heap-based out-of-bounds write. This issue compromises GRUB's sensitive data integrity and may allow bypassing Secure Boot protection.
- CVE-2025-1125High
In the GRUB HFS+ module, an integer overflow vulnerability occurs when calculating buffer sizes based on user-controlled filesystem metadata. This can lead to allocating a smaller buffer than needed and subsequent out-of-bounds write in the hfsplus_open_compressed_real() function.
- CVE-2025-0689High
A heap-based buffer overflow vulnerability in the UDF filesystem module of GRUB allows an attacker to bypass Secure Boot protections. By crafting a malicious filesystem image, arbitrary code execution can be achieved during the boot process.
Original NVD description (English source)
A local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command. GRUB does not validate that the base address corresponds to a UART device, rather than being an arbitrary memory address. This allows an attacker to trick GRUB into writing non-arbitrary data at an attacker-controlled address, including resetting the grub_file_verifiers list in a way that disables the subsequent verification of loaded modules.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS