What’s Vulnerable › Vulnerabilities

CVE-2026-97876: Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address

• Severity: medium (CVSS 6.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-02 · updated 2026-10-02
• Weakness: CWE-822

Description

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.

Affected products

• grub2: from 2.12 before 2.16 — fixed in 2.16

How to fix

Upgrade to a fixed version: grub2 2.16. Check the vendor advisory for mitigations.

References

• https://gitlab.freedesktop.org/gnu-grub/grub/-/commit/26beaa3b2720fefdc4d04c1ae209b776fe6848d6
• https://www.openwall.com/lists/oss-security/2026/09/13/5

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