What’s Vulnerable › Vulnerabilities

CVE-2020-15705: GRUB2: avoid loading unsigned kernels when GRUB is booted directly under secureboot without shim

• Severity: medium (CVSS 6.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-07-29 · updated 2026-06-17
• Weakness: CWE-347

Description

GRUB2 fails to validate kernel signature when booted directly without shim, allowing secure boot to be bypassed. This only affects systems where the kernel signing certificate has been imported directly into the secure boot database and the GRUB image is booted directly without the use of shim. This issue affects GRUB2 version 2.04 and prior versions.

Affected products

• Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 20.04
• Debian Linux: 10.0
• grub2: through 2.04
• Microsoft Windows 10 Version 1607: 1607, 1709, 1803, 1809, 1903, 1909 (+1)
• Microsoft Windows 8.1: all versions
• Microsoft Windows RT 8.1: all versions
• Microsoft Windows Server 2012: r2
• Microsoft Windows Server 2016: 1903, 1909, 2004
• Microsoft Windows Server 2019: all versions
• openSUSE Leap: 15.1, 15.2
• Red Hat Enterprise Linux: 7.0, 8.0
• RedHat Enterprise Linux Atomic Host: all versions
• Red Hat OpenShift Container Platform 4.18: 4.0
• SUSE Linux Enterprise: 11, 12, 15
• Ubuntu grub2 in Ubuntu: from 20.04 LTS before 2.04-1ubuntu26.1; from 18.04 LTS before 2.02-2ubuntu8.16; from 16.04 LTS before 2.02~beta2-36ubuntu3.26; from 14.04 ESM before 2.02~beta2-9ubuntu1.20 — fixed in 2.04-1ubuntu26.1, 2.02-2ubuntu8.16, 2.02~beta2-36ubuntu3.26, 2.02~beta2-9ubuntu1.20

How to fix

Upgrade to a fixed version: Ubuntu grub2 in Ubuntu 2.04-1ubuntu26.1, 2.02-2ubuntu8.16, 2.02~beta2-36ubuntu3.26, 2.02~beta2-9ubuntu1.20. Check the vendor advisory for mitigations.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00067.html
• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00069.html
• http://ubuntu.com/security/notices/USN-4432-1
• http://www.openwall.com/lists/oss-security/2020/07/29/3
• http://www.openwall.com/lists/oss-security/2021/03/02/3
• http://www.openwall.com/lists/oss-security/2021/09/17/2
• http://www.openwall.com/lists/oss-security/2021/09/17/4
• http://www.openwall.com/lists/oss-security/2021/09/21/1
• https://access.redhat.com/security/vulnerabilities/grub2bootloader
• https://lists.gnu.org/archive/html/grub-devel/2020-07/msg00034.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/ADV200011
• https://security.gentoo.org/glsa/202104-05

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