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CVE-2026-97876

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

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 6.4 · Medium · EPSS 0.1% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • grub2

    Versions
    • ≥ 2.12, < 2.16: Affected (semver)

    Update to 2.16

  • grub2 Debian:13

    Versions
    • 2.12-9
    • 2.12-9+deb13u1
    • 2.12-9+deb13u2
    • 2.12-9+hurd.1
    • 2.14-1
    • 2.14-2
    • 2.14-3
    • 2.14-4
    • 2.14~git20250718.0e36779-1
    • 2.14~git20250718.0e36779-2
    • 2.16-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2 Debian:14

    Versions
    • 2.12-9
    • 2.12-9+hurd.1
    • 2.14-1
    • 2.14-2
    • 2.14-3
    • 2.14~git20250718.0e36779-1
    • 2.14~git20250718.0e36779-2
    Affected ranges
    • ECOSYSTEM: < 2.14-4

    Update to 2.14-4

  • grub2 Ubuntu:Pro:14.04:LTS

    Versions
    • 2.00-19ubuntu2
    • 2.00-19ubuntu3
    • 2.00-19ubuntu4
    • 2.00-20
    • 2.00-21
    • 2.00-22
    • 2.02~beta2-5
    • 2.02~beta2-6
    • 2.02~beta2-7
    • 2.02~beta2-8
    • 2.02~beta2-9
    • 2.02~beta2-9ubuntu1
    • 2.02~beta2-9ubuntu1.1
    • 2.02~beta2-9ubuntu1.2
    • 2.02~beta2-9ubuntu1.3
    • 2.02~beta2-9ubuntu1.4
    • 2.02~beta2-9ubuntu1.5
    • 2.02~beta2-9ubuntu1.6
    • 2.02~beta2-9ubuntu1.7
    • 2.02~beta2-9ubuntu1.8
    • 2.02~beta2-9ubuntu1.11
    • 2.02~beta2-9ubuntu1.12
    • 2.02~beta2-9ubuntu1.14
    • 2.02~beta2-9ubuntu1.15
    • 2.02~beta2-9ubuntu1.16
    • 2.02~beta2-9ubuntu1.17
    • 2.02~beta2-9ubuntu1.20
    • 2.02~beta2-9ubuntu1.21
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:Pro:14.04:LTS

    Versions
    • 1.22
    • 1.23
    • 1.24
    • 1.25
    • 1.26
    • 1.27
    • 1.30
    • 1.31
    • 1.32
    • 1.33
    • 1.34
    • 1.34.1
    • 1.34.2
    • 1.34.3
    • 1.34.4
    • 1.34.5
    • 1.34.6
    • 1.34.7
    • 1.34.8
    • 1.34.9
    • 1.34.13
    • 1.34.14
    • 1.34.16
    • 1.34.17
    • 1.34.18
    • 1.34.20
    • 1.34.22
    • 1.34.24
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:16.04:LTS

    Versions
    • 1.55
    • 1.56
    • 1.57
    • 1.58
    • 1.59
    • 1.61
    • 1.62
    • 1.63
    • 1.64
    • 1.65
    • 1.66
    • 1.66.1
    • 1.66.2
    • 1.66.6
    • 1.66.7
    • 1.66.8
    • 1.66.9
    • 1.66.11
    • 1.66.12
    • 1.66.14
    • 1.66.15
    • 1.66.16
    • 1.66.17
    • 1.66.18
    • 1.66.19
    • 1.66.20
    • 1.66.21
    • 1.66.22
    • 1.66.23
    • 1.66.26
    • 1.66.27
    • 1.66.28
    • 1.66.29
    • 1.167~16.04.1
    • 1.167~16.04.2
    • 1.167~16.04.4
    • 1.167~16.04.6
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-unsigned Ubuntu:16.04:LTS

    Versions
    • 2.04-1ubuntu44
    • 2.04-1ubuntu44.1
    • 2.04-1ubuntu44.1.2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:18.04:LTS

    Versions
    • 1.85
    • 1.86
    • 1.87
    • 1.89
    • 1.91
    • 1.92
    • 1.93
    • 1.93.1
    • 1.93.2
    • 1.93.3
    • 1.93.4
    • 1.93.5
    • 1.93.7
    • 1.93.8
    • 1.93.10
    • 1.93.11
    • 1.93.13
    • 1.93.14
    • 1.93.15
    • 1.93.16
    • 1.93.18
    • 1.93.19
    • 1.93.20
    • 1.93.21
    • 1.93.22
    • 1.93.24
    • 1.167~18.04.1
    • 1.167~18.04.3
    • 1.167~18.04.5
    • 1.173.2~18.04.1
    • 1.187.2~18.04.1
    • 1.187.3~18.04.1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-unsigned Ubuntu:18.04:LTS

    Versions
    • 2.04-1ubuntu44
    • 2.04-1ubuntu44.1
    • 2.04-1ubuntu44.1.2
    • 2.04-1ubuntu47.4
    • 2.06-2ubuntu14
    • 2.06-2ubuntu14.1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:20.04:LTS

    Versions
    • 1.128
    • 1.129
    • 1.130
    • 1.131
    • 1.133
    • 1.134
    • 1.135
    • 1.136
    • 1.137
    • 1.138
    • 1.139
    • 1.140
    • 1.141
    • 1.142
    • 1.142.1
    • 1.142.3
    • 1.142.4
    • 1.142.5
    • 1.142.6
    • 1.142.8
    • 1.142.9
    • 1.142.10
    • 1.142.11
    • 1.167
    • 1.167.2
    • 1.173.2~20.04.1
    • 1.173.4
    • 1.187.2~20.04.2
    • 1.187.3~20.04.1
    • 1.187.4~20.04.1
    • 1.187.6~20.04.1
    • 1.187.12~20.04
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-unsigned Ubuntu:20.04:LTS

    Versions
    • 2.04-1ubuntu44
    • 2.04-1ubuntu44.2
    • 2.04-1ubuntu47.4
    • 2.04-1ubuntu47.5
    • 2.06-2ubuntu14
    • 2.06-2ubuntu14.1
    • 2.06-2ubuntu14.2
    • 2.06-2ubuntu14.4
    • 2.06-2ubuntu14.8
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:22.04:LTS

    Versions
    • 1.173
    • 1.174
    • 1.176
    • 1.177
    • 1.178
    • 1.179
    • 1.180
    • 1.182~22.04.1
    • 1.187.2
    • 1.187.3~22.04.1
    • 1.187.4~22.04.1
    • 1.187.6
    • 1.187.12
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-unsigned Ubuntu:22.04:LTS

    Versions
    • 2.04-1ubuntu47
    • 2.04-1ubuntu48
    • 2.06-2ubuntu3
    • 2.06-2ubuntu4
    • 2.06-2ubuntu5
    • 2.06-2ubuntu6
    • 2.06-2ubuntu7
    • 2.06-2ubuntu10
    • 2.06-2ubuntu14
    • 2.06-2ubuntu14.1
    • 2.06-2ubuntu14.2
    • 2.06-2ubuntu14.4
    • 2.06-2ubuntu14.8
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:24.04:LTS

    Versions
    • 1.197
    • 1.199
    • 1.201
    • 1.202
    • 1.202.2
    • 1.202.5
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-unsigned Ubuntu:24.04:LTS

    Versions
    • 2.12~rc1-10ubuntu4
    • 2.12~rc1-12ubuntu2
    • 2.12-1ubuntu1
    • 2.12-1ubuntu7
    • 2.12-1ubuntu7.1
    • 2.12-1ubuntu7.3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:26.10

    Versions
    • 1.215
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-unsigned Ubuntu:26.10

    Versions
    • 2.14-2ubuntu1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-signed Ubuntu:26.04:LTS

    Versions
    • 1.214
    • 1.215
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • grub2-unsigned Ubuntu:26.04:LTS

    Versions
    • 2.14~git20250718.0e36779-1ubuntu4
    • 2.14-2ubuntu1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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