CVE-2021-25736: Windows kube-proxy LoadBalancer contention
First published: Mon 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.
Credit: jordan@liggitt.net jordan@liggitt.net
| Affected Software | Affected Version | How to fix |
|---|---|---|
| go/k8s.io/kubernetes | <1.21 | 1.21 |
| All of | ||
| Any of | ||
| 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 |
Remedy
This issue has been fixed in the following versions: * v1.21.0 * v1.20.6 * v1.19.10 * v1.18.18
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Reference Links
- https://github.com/kubernetes/kubernetes/pull/99958
- https://groups.google.com/g/kubernetes-security-announce/c/lIoOPObO51Q/m/O15LOazPAgAJ
- https://nvd.nist.gov/vuln/detail/CVE-2021-25736
- https://github.com/kubernetes/kubernetes/commit/b014610de3e5cf1bb0f7844b5758d29fc18b75e6
- https://github.com/advisories/GHSA-35c7-w35f-xwgh (Advisory)
- https://security.netapp.com/advisory/ntap-20231221-0003/
Frequently Asked Questions
What is the severity of CVE-2021-25736?
The severity of CVE-2021-25736 is medium, with a severity value of 5.8.
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.
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.
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.
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].
- collector/nvd-cve
- collector/github-advisory-latest
- alias/GHSA-35c7-w35f-xwgh
- alias/CVE-2021-25736
- collector/github-advisory
- collector/nvd-api
- agent/author
- agent/type
- agent/softwarecombine
- agent/first-publish-date
- collector/mitre-cve
- source/MITRE
- agent/last-modified-date
- agent/references
- agent/severity
- agent/remedy
- agent/title
- agent/description
- agent/event
- agent/trending
- agent/tags
- agent/source
- package-manager/go
- vendor/kubernetes
- canonical/kubernetes kubernetes
- version/kubernetes kubernetes/1.18.0
- version/kubernetes kubernetes/1.19.0
- version/kubernetes kubernetes/1.20.0
- vendor/microsoft
- canonical/microsoft windows