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KubernetesApplication

CVE-2021-25749

HIGH · 7.8 CVSS v3.1 Published 2023-05-24
Fix available
A fix is available. Upgrade to 1.22.14 / 1.23.11 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
Windows workloads can run as ContainerAdministrator even when those workloads set the runAsNonRoot option to true.

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

In Kubernetes clusters with Windows worker nodes, the security context option runAsNonRoot is not properly enforced. When set to true, this option is intended to prevent containers from running as root. However, Windows containers bypass this setting and run as ContainerAdministrator (equivalent to root on Windows), allowing workloads to execute with elevated privileges despite the runAsNonRoot configuration.

MitigationEnsure Windows workloads do not require ContainerAdministrator privileges. Review and enforce non-root user configurations through alternative security controls such as pod security policies/admissions, node selectors to Linux, or application redesign to avoid Windows admin requirements. Consider upgrading Kubernetes to versions that address this enforcement gap.

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
KubernetesApplication
Affected:>= 1.20.0, <= 1.21.0>= 1.22.0, < 1.22.14>= 1.23.0, < 1.23.11>= 1.24.0, < 1.24.5

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 Kubernetes control plane version
    Run 'kubectl version --short' or 'kubectl get nodes' to identify the API server and controller manager versions
    Affected if The Kubernetes version falls within >= 1.20.0 <= 1.21.0, >= 1.22.0 < 1.22.14, >= 1.23.0 < 1.23.11, or >= 1.24.0 < 1.24.5
  2. Identify Windows worker nodes
    Run 'kubectl get nodes -o jsonpath="{.items[?(@.status.nodeInfo.osImage!='')].metadata.name},{.items[?(@.status.nodeInfo.osImage!='')].status.nodeInfo.osImage}"' and look for Windows Server in the output
    Affected if The cluster contains Windows worker nodes running Windows containers
  3. Find pods with runAsNonRoot enabled on Windows containers
    Review pod specs: run 'kubectl get pods --all-namespaces -o json' and search for containers where securityContext.runAsNonRoot is set to true and the nodeSelector includes Windows or the container image is Windows-based
    Affected if Pods exist with runAsNonRoot: true configured for Windows containers
  4. Verify actual container user privilege level
    Exec into a Windows container and run 'whoami /groups' or check the effective user ID from within the container using 'id' command
    Affected if The container runs as ContainerAdministrator or shows elevated privileges despite runAsNonRoot being set to true

The environment is affected if the Kubernetes version is in the affected range, the cluster has Windows worker nodes, and Windows pods are configured with runAsNonRoot: true but actually run with elevated ContainerAdministrator privileges.

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 1.22.14 / 1.23.11 / 1.24.5 or later
Fixed in 1.22.141.23.111.24.5
Interim mitigation

Ensure Windows workloads do not require ContainerAdministrator privileges. Review and enforce non-root user configurations through alternative security controls such as pod security policies/admissions, node selectors to Linux, or application redesign to avoid Windows admin requirements. Consider upgrading Kubernetes to versions that address this enforcement gap.

Recommended fix High confidence

Kubernetes 1.22.14, 1.23.11, or 1.24.5 (depending on your current minor version)

  1. 1. Identify the current Kubernetes cluster version by running: kubectl version --short or checking the control plane nodes
  2. 2. Plan the upgrade path: if on 1.20.x or 1.21.x, upgrade to 1.21.11 or later; if on 1.22.x, upgrade to 1.22.14; if on 1.23.x, upgrade to 1.23.11; if on 1.24.x, upgrade to 1.24.5
  3. 3. Review Kubernetes release notes for your target version to check for breaking changes and API deprecations
  4. 4. Backup etcd data and cluster state before initiating the upgrade
  5. 5. Upgrade the control plane nodes first, following your cluster's upgrade procedure (e.g., kubeadm upgrade apply for kubeadm clusters)
  6. 6. Upgrade worker nodes after control plane is healthy
  7. 7. Verify the upgrade completed successfully: kubectl get nodes and confirm all nodes show the new version
  8. 8. For Windows workloads, verify that the runAsNonRoot setting is properly enforced by deploying a test pod with runAsNonRoot: true and confirming it does not run as ContainerAdministrator
Caveat Review release notes for your target version as Kubernetes upgrades may include API deprecations, kubelet changes, and feature flag modifications that could affect workload behavior

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

Fix this in Kubernetes Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
36.0 hours of engineering $6,400
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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-2021-25749 in production — separate from our analysis above.

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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
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  • Version or environment caveats, and links to real fixes
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