CVE-2021-25736: Windows kube-proxy LoadBalancer contention

Published Oct 30, 2023
·
Updated

Kube-proxy on Windows can unintentionally forward traffic to local processes listening on the same port (“spec.ports[].port”) as a LoadBalancer Service when the LoadBalancer controller does not set the “status.loadBalancer.ingress[].ip” field. Clusters where the LoadBalancer controller sets the “status.loadBalancer.ingress[].ip” field are unaffected.

Other sources

Kube-proxy on Windows can unintentionally forward traffic to local processes listening on the same port (spec.ports[].port) as a LoadBalancer Service when the LoadBalancer controller does not set the status.loadBalancer.ingress[].ip field. Clusters where the LoadBalancer controller sets the status.loadBalancer.ingress[].ip field are unaffected.

— GitHub

Affected Software

6 affected componentsFixes available
go/k8s.io/kubernetes<1.21
1.21
All of the following
Any of the following
Kubernetes kubernetes>=1.18.0<1.18.18
Kubernetes kubernetes>=1.19.0<1.19.10
Kubernetes kubernetes>=1.20.0<1.20.6
Microsoft Windows
IBM Netezza Software<=11.3.0.3-IF2

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade go/k8s.io/kubernetes to a version that resolves this vulnerability.

    Fixed in 1.21
  2. Upgrade

    Upgrade kube-proxy (Windows) to a version that resolves this vulnerability.

    Fixed in v1.18.18
  3. Upgrade

    Upgrade kube-proxy (Windows) to a version that resolves this vulnerability.

    Fixed in v1.19.10
  4. Upgrade

    Upgrade kube-proxy (Windows) to a version that resolves this vulnerability.

    Fixed in v1.20.6
  5. Upgrade

    Upgrade kube-proxy (Windows) to a version that resolves this vulnerability.

    Fixed in v1.21.0

Event History

Oct 30, 2023
CVE Published
via MITRE·02:19 AM
Data Sourced
via MITRE·02:19 AM
RemedyDescriptionSeverity
Data Sourced
03:15 AM
DescriptionSeverity
Advisory Published
via GitHub·03:30 AM
Aug 20, 2026
Data Sourced
via IBM·12:00 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Frequently Asked Questions

1

What is the severity of CVE-2021-25736?

The severity of CVE-2021-25736 is medium, with a severity value of 5.8.

2

How does CVE-2021-25736 affect Windows kube-proxy?

CVE-2021-25736 affects Windows kube-proxy by unintentionally forwarding traffic to local processes listening on the same port as a LoadBalancer Service when the LoadBalancer controller does not set the 'status.loadBalancer.ingress[].ip' field.

3

Which version of k8s.io/kubernetes is affected by CVE-2021-25736?

CVE-2021-25736 affects version up to, but not including, 1.21 of k8s.io/kubernetes.

4

How can I fix CVE-2021-25736?

To fix CVE-2021-25736, update to a version of k8s.io/kubernetes that is 1.21 or newer.

5

Where can I find more information about CVE-2021-25736?

You can find more information about CVE-2021-25736 at the following references: [link1], [link2], [link3].

Company

Resources

Contact

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