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Fencer Vulns
medium 6.5

CVE-2020-26541 json

The Linux kernel through 5.8.13 does not properly enforce the Secure Boot Forbidden Signature Database (aka dbx) protection mechanism.

published 2020-10-02 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-19086

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

The Linux kernel through 5.8.13 does not properly enforce the Secure Boot Forbidden Signature Database (aka dbx) protection mechanism. This affects certs/blacklist.c and certs/system_keyring.c.

Patch / fix

  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2020-26541

  • linux Ubuntu 20.04 LTS 5.4.0-92.103
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1061.64
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1059.63
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1057.60
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1010.11
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1051.53
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1065.68
  • linux-gkeop Ubuntu 20.04 LTS 5.4.0-1029.30

ubuntu advisories UBUNTU-CVE-2020-26541

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-rt RHEL 8 4.18.0-305.7.1.rt7.79.el8_4
  • kernel-rt-kvm RHEL 8 4.18.0-305.7.1.rt7.79.el8_4
  • kernel-rt-core RHEL 8 4.18.0-305.7.1.rt7.79.el8_4
  • kernel-rt-modules RHEL 8 4.18.0-305.7.1.rt7.79.el8_4
  • kernel-rt-debug-kvm RHEL 8 4.18.0-305.7.1.rt7.79.el8_4
  • kernel-rt-debug-core RHEL 8 4.18.0-305.7.1.rt7.79.el8_4
  • kernel-rt-debug-modules RHEL 8 4.18.0-305.7.1.rt7.79.el8_4
  • kernel-rt-modules-extra RHEL 8 4.18.0-305.7.1.rt7.79.el8_4

red hat advisories RHSA-2021:2666RHSA-2021:2719RHSA-2021:2599RHSA-2021:2718RHSA-2021:2570

  • kernel-syms SLES 12 SP3-BCL 4.4.180-94.182.1
  • kernel-source SLES 12 SP3-BCL 4.4.180-94.182.1
  • kernel-default SLES 12 SP3-BCL 4.4.180-94.182.1
  • kernel-syms SLES 12 SP2-BCL 4.4.121-92.196.2
  • kernel-source SLES 12 SP2-BCL 4.4.121-92.196.2
  • kernel-default SLES 12 SP2-BCL 4.4.121-92.196.2
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.94.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.94.1

suse advisories SUSE-SU-2022:4611-1SUSE-SU-2022:4561-1SUSE-SU-2022:2629-1SUSE-SU-2022:2407-1SUSE-SU-2022:2393-1SUSE-SU-2022:2382-1

  • kernel-rt openSUSE Leap Micro 5.2 5.3.18-150300.93.1
  • kernel-default openSUSE Leap Micro 5.2 5.3.18-150300.59.76.1
  • kernel-default-base openSUSE Leap Micro 5.2 5.3.18-150300.59.76.1.150300.18.45.2

opensuse advisories openSUSE-SU-2022:2177-1openSUSE-SU-2022:2173-1

  • kernel Rocky Linux 8 4.18.0-305.7.1.el8_4

rocky linux advisories RLSA-2021:2570

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-26541 updated cvss 6.5

kernel: security bypass in certs/blacklist.c and certs/system_keyring.c

  • Red Hat Enterprise Linux 7 kernel-alt
    affected: workaround, no fix planned “Will not fix”
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-305.7.1.el8_4, kernel-debuginfo-common-aarch64 4.18.0-305.7.1.el8_4, kernel-debuginfo-common-ppc64le 4.18.0-305.7.1.el8_4
    fixed: vendor fix RHSA-2021:2570
  • Red Hat CodeReady Linux Builder EUS (v. 8.1) kernel-debuginfo-common-x86_64 4.18.0-147.51.1.el8_1, kernel-debuginfo-common-aarch64 4.18.0-147.51.1.el8_1, kernel-debuginfo-common-ppc64le 4.18.0-147.51.1.el8_1
    fixed: vendor fix RHSA-2021:2666
  • Red Hat CodeReady Linux Builder EUS (v. 8.2) kernel-debuginfo-common-x86_64 4.18.0-193.60.2.el8_2, kernel-debuginfo-common-aarch64 4.18.0-193.60.2.el8_2, kernel-debuginfo-common-ppc64le 4.18.0-193.60.2.el8_2
    fixed: vendor fix RHSA-2021:2718
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-305.7.1.el8_4, kernel 4.18.0-305.7.1.el8_4, bpftool 4.18.0-305.7.1.el8_4, kernel-core 4.18.0-305.7.1.el8_4, kernel-tools 4.18.0-305.7.1.el8_4, python3-perf 4.18.0-305.7.1.el8_4, +15 more
    fixed: vendor fix RHSA-2021:2570
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.1) perf 4.18.0-147.51.1.el8_1, kernel 4.18.0-147.51.1.el8_1, bpftool 4.18.0-147.51.1.el8_1, kernel-core 4.18.0-147.51.1.el8_1, kernel-tools 4.18.0-147.51.1.el8_1, python3-perf 4.18.0-147.51.1.el8_1, +15 more
    fixed: vendor fix RHSA-2021:2666
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.2) perf 4.18.0-193.60.2.el8_2, kernel 4.18.0-193.60.2.el8_2, bpftool 4.18.0-193.60.2.el8_2, kernel-core 4.18.0-193.60.2.el8_2, kernel-tools 4.18.0-193.60.2.el8_2, python3-perf 4.18.0-193.60.2.el8_2, +15 more
    fixed: vendor fix RHSA-2021:2718
  • Red Hat Enterprise Linux Real Time (v. 8) kernel-rt 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-core 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-modules 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-debug-core 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-debug-modules 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-modules-extra 4.18.0-305.7.1.rt7.79.el8_4, +2 more
    fixed: vendor fix RHSA-2021:2599
show 5 more
  • Red Hat Enterprise Linux Real Time EUS (v. 8.2) kernel-rt 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-core 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-modules 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-debug-core 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-debug-modules 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-modules-extra 4.18.0-193.60.2.rt13.112.el8_2, +2 more
    fixed: vendor fix RHSA-2021:2719
  • Red Hat Enterprise Linux Real Time for NFV (v. 8) kernel-rt 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-kvm 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-core 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-modules 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-debug-kvm 4.18.0-305.7.1.rt7.79.el8_4, kernel-rt-debug-core 4.18.0-305.7.1.rt7.79.el8_4, +4 more
    fixed: vendor fix RHSA-2021:2599
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 8.2) kernel-rt 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-kvm 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-core 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-modules 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-debug-kvm 4.18.0-193.60.2.rt13.112.el8_2, kernel-rt-debug-core 4.18.0-193.60.2.rt13.112.el8_2, +4 more
    fixed: vendor fix RHSA-2021:2719
  • Red Hat Migration Toolkit 1.4 rhmtc/openshift-migration-ui-rhel8 v1.4.6-4, rhmtc/openshift-velero-plugin-rhel8 v1.4.6-4, rhmtc/openshift-migration-velero-rhel8 v1.4.6-5, rhmtc/openshift-migration-registry-rhel8 v1.4.6-4, rhmtc/openshift-migration-operator-bundle v1.4.6-5, rhmtc/openshift-migration-controller-rhel8 v1.4.6-4, +7 more
    fixed: vendor fix RHBA-2021:2854
  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +81 more Red Hat Enterprise MRG 2 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.53% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • lkml.org https://lkml.org/lkml/2020/9/15/1871 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AC:L/AV:L/A:H/C:H/I:H/PR:H/S:U/UI:R
CNA 3.1 6.5 CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:H
NVD 3.1 6.5 CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 6.9 AV:L/AC:M/Au:N/C:C/I:C/A:C

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.