CVE-2019-20908

Severity: medium (CVSS 6.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-07-15 · updated 2026-06-17

Description

An issue was discovered in drivers/firmware/efi/efi.c in the Linux kernel before 5.4. Incorrect access permissions for the efivar_ssdt ACPI variable could be used by attackers to bypass lockdown or secure boot restrictions, aka CID-1957a85b0032.

Affected products

Canonical Ubuntu Linux: 16.04, 18.04
Linux kernel: before 5.4 — fixed in 5.4
openSUSE Leap: 15.1

How to fix

Upgrade to a fixed version: Linux kernel 5.4. Check the vendor advisory for mitigations.

References

http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00009.html
http://www.openwall.com/lists/oss-security/2020/07/20/6
http://www.openwall.com/lists/oss-security/2020/07/29/3
http://www.openwall.com/lists/oss-security/2020/07/30/2
http://www.openwall.com/lists/oss-security/2020/07/30/3
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.4
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1957a85b0032a81e6482ca4aab883643b8dae06e
https://git.zx2c4.com/american-unsigned-language/tree/american-unsigned-language.sh
https://mailarchives.bentasker.co.uk/Mirrors/OSSSec/2020/06-Jun/msg00035.html
https://usn.ubuntu.com/4426-1/
https://usn.ubuntu.com/4427-1/
https://usn.ubuntu.com/4439-1/

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