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Linux KernelOperating system · Linux

CVE-2021-4197

HIGH · 7.8 CVSS v3.1 Published 2022-03-23
Fix available
A fix is available. Upgrade to 4.14.276 / 4.19.238 or later.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A local privilege escalation vulnerability in the Linux kernel's control groups (cgroup) subsystem allows an unprivileged user to write to file handlers in a way that can be exploited. The flaw affects both cgroup1 and cgroup2 implementations and enables a local attacker to potentially crash the system or escalate privileges to root by manipulating cgroup configurations.

MitigationApply the relevant Linux kernel security patch; most distributions have released updates. Until patched, limit local untrusted user access to systems and monitor for suspicious cgroup activity.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 4.2, < 4.14.276>= 4.15, < 4.19.238>= 4.20, < 5.4.189>= 5.5, < 5.10.111>= 5.11, < 5.15.14
Debian LinuxOperating system
Affected:= 10.0
Communications Cloud Native Core Binding Support FunctionApplication
Affected:= 22.1.1= 22.1.3= 22.2.0
Brocade Fabric Operating System FirmwareOperating system
Affected:all versions
H300s FirmwareOperating system
Affected:all versions
H500s FirmwareOperating system
Affected:all versions
H700s FirmwareOperating system
Affected:all versions
H410s FirmwareOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check your Linux kernel version
    Run `uname -r` to get the installed kernel version, then compare it against the affected ranges: < 4.14.276, >= 4.15 and < 4.19.238, >= 4.20 and < 5.4.189, >= 5.5 and < 5.10.111, >= 5.11 and < 5.15.14
    Affected if The kernel version falls within any of the affected ranges listed above
  2. Verify cgroup is enabled on the system
    Run `mount | grep -E 'cgroup|cgroup2'` or check `cat /proc/cgroups` to see if cgroup or cgroup2 filesystems are mounted and active
    Affected if Cgroup1 or cgroup2 is mounted and the kernel version is vulnerable (the vulnerability affects both cgroup implementations)
  3. Identify untrusted local user accounts
    Check `/etc/passwd` for non-system user accounts (UID >= 1000) and review who has shell access via `who` or `last` commands
    Affected if There are unprivileged local users on the system and the kernel is vulnerable; the flaw requires an unprivileged user to trigger the exploitation
  4. Check product-specific firmware versions for affected devices
    For Netapp H300s/H500s/H700s/H410s, Broadcom Fabric OS, Oracle Communications Binding Support Function, or Debian 10 systems, determine the exact firmware or OS version using vendor-specific commands or documentation
    Affected if The product version matches exactly the affected versions listed in the CVE (Debian 10.0, Oracle BSF 22.1.1/22.1.3/22.2.0, or any Broadcom/Netapp firmware version)

You are affected if your Linux kernel version is within the affected ranges AND cgroup is enabled AND untrusted local users exist on the system, or if you run any of the specific affected product versions listed.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.14.276 / 4.19.238 / 5.4.189 or later
Fixed in 4.14.2764.19.2385.4.189
Interim mitigation

Apply the relevant Linux kernel security patch; most distributions have released updates. Until patched, limit local untrusted user access to systems and monitor for suspicious cgroup activity.

Recommended fix High confidence

Linux Kernel 4.14.276 / 4.19.238 / 5.4.189 / 5.10.111 or later stable release

  1. Check the currently running kernel version using `uname -r` or `cat /proc/version`
  2. Identify your distribution and its package manager (e.g., apt for Debian/Ubuntu, yum/dnf for RHEL/Fedora, zypper for SUSE)
  3. Update your package repository metadata: `sudo apt update` (Debian/Ubuntu) or `sudo yum check-update` (RHEL) or `sudo dnf check-update` (Fedora)
  4. Install the updated kernel package: `sudo apt install linux-image-<version>` or `sudo yum install kernel-<version>` or `sudo dnf install kernel-<version>`
  5. Reboot the system to load the new kernel: `sudo reboot`
  6. Verify the new kernel is running after reboot using `uname -r`
  7. For Debian 10 (buster), ensure backports or security updates are enabled in /etc/apt/sources.list to receive kernel updates
Caveat Kernel upgrades may require system reboot and could cause issues with proprietary kernel modules or drivers that are not compatible with the new version; verify critical modules/driver compatibility before upgrading production systems

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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Scan for this in your stack

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dbcve dependency scanner

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-4197 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data