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Fencer Vulns
high 7.8

CVE-2021-4197 json

An unprivileged write to the file handler flaw in the Linux kernel's control groups and namespaces subsystem was found in the way users hav…

published 2022-03-23 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-34056

cvss
7.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits
0
none known

Summary

An unprivileged write to the file handler flaw in the Linux kernel's control groups and namespaces subsystem was found in the way users have access to some less privileged process that are controlled by cgroups and have higher privileged parent process. It is actually both for cgroup2 and cgroup1 versions of control groups. A local user could use this flaw to crash the system or escalate their privileges on the system.

Patch / fix

  • linux linux_kernel 4.14.276, 4.19.238, 5.4.189, 5.10.111, 5.15.14
  • linux Debian 14, Debian 13, Debian 12 5.15.15-1

debian advisories DEBIAN-CVE-2021-4197

  • linux Ubuntu 18.04 LTS 4.15.0-189.200
  • linux Ubuntu 20.04 LTS 5.4.0-117.132
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1137.148
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1078.84
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1078.84
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1074.79
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1026.29
  • linux-iot Ubuntu 20.04 LTS 5.4.0-1004.6

ubuntu advisories UBUNTU-CVE-2021-4197

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 RHEL 8 4.18.0-372.9.1.el8
  • perf RHEL 8 4.18.0-372.9.1.el8
  • bpftool RHEL 8 4.18.0-372.9.1.el8
  • kernel-core RHEL 8 4.18.0-372.9.1.el8
  • kernel-tools RHEL 8 4.18.0-372.9.1.el8
  • python3-perf RHEL 8 4.18.0-372.9.1.el8
  • kernel-modules RHEL 8 4.18.0-372.9.1.el8
  • kernel-zfcpdump RHEL 8 4.18.0-372.9.1.el8

red hat advisories RHSA-2022:1988RHSA-2022:5626RHSA-2022:5633RHSA-2022:1975

  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-syms SLES 12 SP2-BCL 4.4.121-92.164.1
  • kernel-source SLES 12 SP2-BCL 4.4.121-92.164.1
  • kernel-default SLES 12 SP2-BCL 4.4.121-92.164.1
  • kernel-azure SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-16.88.1

suse advisories SUSE-SU-2022:0555-1SUSE-SU-2022:0477-1SUSE-SU-2022:0372-1SUSE-SU-2022:0371-1SUSE-SU-2022:0367-1SUSE-SU-2022:0366-1

  • kernel-default openSUSE Leap 15.3 4.12.14-197.105.1
  • kernel-vanilla openSUSE Leap 15.3 4.12.14-197.105.1
  • kernel-kvmsmall openSUSE Leap 15.3 4.12.14-197.105.1
  • kernel-zfcpdump openSUSE Leap 15.3 4.12.14-197.105.1
  • dtb-aarch64 openSUSE Leap 15.3 5.3.18-150300.59.43.1
  • kernel-64kb openSUSE Leap 15.3 5.3.18-150300.59.43.1
  • kernel-syms openSUSE Leap 15.3 5.3.18-150300.59.43.1
  • kernel-obs-qa openSUSE Leap 15.3 5.3.18-150300.59.43.1

opensuse advisories openSUSE-SU-2022:0366-1openSUSE-SU-2022:0198-1openSUSE-SU-2022:0169-1

  • kernel AlmaLinux 8 4.18.0-372.9.1.el8
  • perf AlmaLinux 8 4.18.0-372.9.1.el8
  • bpftool AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-core AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-tools AlmaLinux 8 4.18.0-372.9.1.el8
  • python3-perf AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-modules AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-debug-core AlmaLinux 8 4.18.0-372.9.1.el8

almalinux advisories ALSA-2022:1988

  • kernel Rocky Linux 8 4.18.0-372.9.1.el8
  • kernel-rt Rocky Linux 8 4.18.0-372.9.1.rt7.166.el8

rocky linux advisories RLSA-2022:1988RLSA-2022:1975

  • kernel CBL-Mariner 2.0 5.15.37.1-2

azure linux advisories AZL-9141

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • linux Arch Linux 5.17.3.arch1-1
  • linux-zen Arch Linux 5.17.3.zen1-1
  • linux-hardened Arch Linux 5.17.5.hardened1-1

arch linux advisories AVG-2698AVG-2699AVG-2700

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-2021-4197 updated cvss 6.3

kernel: cgroup: Use open-time creds and namespace for migration perm checks

  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-372.9.1.el8, kernel 4.18.0-372.9.1.el8, bpftool 4.18.0-372.9.1.el8, kernel-core 4.18.0-372.9.1.el8, kernel-tools 4.18.0-372.9.1.el8, python3-perf 4.18.0-372.9.1.el8, +15 more
    fixed: vendor fix RHSA-2022:1988
  • Red Hat Enterprise Linux BaseOS EUS (v.8.4) perf 4.18.0-305.57.1.el8_4, kernel 4.18.0-305.57.1.el8_4, bpftool 4.18.0-305.57.1.el8_4, kernel-core 4.18.0-305.57.1.el8_4, kernel-tools 4.18.0-305.57.1.el8_4, python3-perf 4.18.0-305.57.1.el8_4, +15 more
    fixed: vendor fix RHSA-2022:5626
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-372.9.1.el8, kernel-debuginfo-common-aarch64 4.18.0-372.9.1.el8, kernel-debuginfo-common-ppc64le 4.18.0-372.9.1.el8
    fixed: vendor fix RHSA-2022:1988
  • Red Hat Enterprise Linux CRB EUS (v.8.4) kernel-debuginfo-common-x86_64 4.18.0-305.57.1.el8_4, kernel-debuginfo-common-aarch64 4.18.0-305.57.1.el8_4, kernel-debuginfo-common-ppc64le 4.18.0-305.57.1.el8_4
    fixed: vendor fix RHSA-2022:5626
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-372.9.1.rt7.166.el8, kernel-rt-kvm 4.18.0-372.9.1.rt7.166.el8, kernel-rt-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-kvm 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-core 4.18.0-372.9.1.rt7.166.el8, +4 more
    fixed: vendor fix RHSA-2022:1975
  • Red Hat Enterprise Linux NFV EUS (v.8.4) kernel-rt 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-kvm 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-core 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-modules 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-debug-kvm 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-debug-core 4.18.0-305.57.1.rt7.129.el8_4, +4 more
    fixed: vendor fix RHSA-2022:5633
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-372.9.1.rt7.166.el8, kernel-rt-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules-extra 4.18.0-372.9.1.rt7.166.el8, +2 more
    fixed: vendor fix RHSA-2022:1975
  • Red Hat Enterprise Linux RT EUS (v.8.4) kernel-rt 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-core 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-modules 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-debug-core 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-debug-modules 4.18.0-305.57.1.rt7.129.el8_4, kernel-rt-modules-extra 4.18.0-305.57.1.rt7.129.el8_4, +2 more
    fixed: vendor fix RHSA-2022:5633
show 1 more
  • 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, +82 more
    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

0.54% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • n/a kernel

Classification

Weakness
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.