kernel: lockdown: bypass through ACPI write via efivar_ssdt
Published Jul 15, 2020
6.7
MEDIUMCVSS 3.1
EPSS 0.51%
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
No data.
Configuration 1
- < 5.4
Configuration 3
- 16.04
- 18.04
No data.
Red Hat Enterprise Linux 8
kernel-0:4.18.0-193.14.3.el8_2
Fixed · RHSA-2020:3218
Red Hat Enterprise Linux 8
kernel-rt-0:4.18.0-193.14.3.rt13.67.el8_2
Fixed · RHSA-2020:3219
Red Hat Enterprise Linux 8.0 Update Services for SAP Solutions
kernel-0:4.18.0-80.27.2.el8_0
Fixed · RHSA-2020:3228
Red Hat Enterprise Linux 8.1 Extended Update Support
kernel-0:4.18.0-147.24.2.el8_1
Fixed · RHSA-2020:3222
Red Hat Enterprise Linux 5
kernel
Not affected
Red Hat Enterprise Linux 6
kernel
Not affected
Red Hat Enterprise Linux 7
kernel
Not affected
Red Hat Enterprise Linux 7
kernel-alt
Not affected
Red Hat Enterprise Linux 7
kernel-rt
Not affected
Red Hat Enterprise MRG 2
kernel-rt
Not affected
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 8 | kernel-0:4.18.0-193.14.3.el8_2 | Fixed | RHSA-2020:3218 |
| Red Hat Enterprise Linux 8 | kernel-rt-0:4.18.0-193.14.3.rt13.67.el8_2 | Fixed | RHSA-2020:3219 |
| Red Hat Enterprise Linux 8.0 Update Services for SAP Solutions | kernel-0:4.18.0-80.27.2.el8_0 | Fixed | RHSA-2020:3228 |
| Red Hat Enterprise Linux 8.1 Extended Update Support | kernel-0:4.18.0-147.24.2.el8_1 | Fixed | RHSA-2020:3222 |
| Red Hat Enterprise Linux 5 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 6 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-alt | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise MRG 2 | kernel-rt | Not affected | n/a |
No package ranges for this CVE.
Remediation
Red Hat statement
This issue is rated as having Moderate impact because of the privileges required for exploitation.
Red Hat mitigation
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
1 other source (Red Hat) ▾
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
No CVSS v3.0 score for this CVE.
AV:L/AC:M/Au:N/C:C/I:C/A:C
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 4, 2026.
Score over time
2021-2026- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Percentile over time
- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Table of values (14 key points)
Flat stretches are collapsed. Showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 4, 2026 | 0.51% (0.00514) | 41.75th | v5 (v2026.06.15) |
| Jun 15, 2026 | 0.51% (0.00514) | 39.48th | v5 (v2026.06.15) |
| Mar 17, 2025 | 0.02% (0.00024) | 3.79th | v4 (v2025.03.14) |
| Dec 12, 2024 | 0.05% (0.00047) | 19.18th | v3 (v2023.03.01) |
| May 7, 2024 | 0.05% (0.00047) | 16.19th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.05% (0.00047) | 14.16th | v3 (v2023.03.01) |
| Mar 6, 2023 | 1.79% (0.01791) | 77.00th | v2 (v2022.01.01) |
| Feb 23, 2023 | 1.79% (0.01791) | 76.95th | v2 (v2022.01.01) |
| Apr 1, 2022 | 1.79% (0.01791) | 74.90th | v2 (v2022.01.01) |
| Feb 4, 2022 | 6.71% (0.06713) | 78.74th | v2 (v2022.01.01) |
| Feb 3, 2022 | 11.74% (0.11741) | 88.45th | v1 |
| Jan 6, 2022 | 11.74% (0.11741) | 88.31th | v1 |
| Sep 1, 2021 | 2.88% (0.02880) | 80.71th | v1 |
| Apr 14, 2021 | 2.88% (0.02880) | 0.00th | v1 |
References (19)
- http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00009.html vendor-advisoryx_refsource_SUSEMailing ListThird Party Advisory
- http://www.openwall.com/lists/oss-security/2020/07/20/6 mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- http://www.openwall.com/lists/oss-security/2020/07/29/3 mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- http://www.openwall.com/lists/oss-security/2020/07/30/2 mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- http://www.openwall.com/lists/oss-security/2020/07/30/3 mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- https://access.redhat.com/security/cve/CVE-2019-20908 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1852942 Issue Tracking
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.4 x_refsource_MISCRelease NotesVendor Advisory
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1957a85b0032a81e6482ca4aab883643b8dae06e x_refsource_MISCPatchVendor Advisory
- https://git.zx2c4.com/american-unsigned-language/tree/american-unsigned-language.sh x_refsource_MISCPatchThird Party Advisory
- https://lore.kernel.org/linux-efi/20200615202408.2242614-1-pjones@redhat.com/
- https://mailarchives.bentasker.co.uk/Mirrors/OSSSec/2020/06-Jun/msg00035.html x_refsource_MISCMailing ListThird Party Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2019-20908
- https://usn.ubuntu.com/4426-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/4427-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/4439-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/4440-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2019-20908
- https://www.openwall.com/lists/oss-security/2020/06/14/1
Change history (0)
No recorded changes yet.