CVE-2020-8558: Improper Authentication in Kubernetes
Summary
CVE-2020-8558: Improper Authentication in Kubernetes. Affects k8s.io/kubernetes across 3 version ranges.
< 1.16.11
>= 1.17.0, < 1.17.7
>= 1.18.0, < 1.18.4
Fixed in 1.16.11, 1.17.7 or 1.18.4, depending on the release line you run. How to fix ↓
Also tracked for
- kubernetes · Debian:11
The same CVE-2020-8558 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. It consists of various components, including the Kubelet and kube-proxy. The Kubelet is responsible for managing the containers running on a node, while kube-proxy enables network communication between services. Kubernetes is widely used in cloud-native environments to streamline application deployment and management.
Vulnerability Detail
The discovered security issue in Kubernetes affects the Kubelet and kube-proxy components. It allows adjacent hosts to access TCP and UDP services bound to 127.0.0.1 on the node or in the node's network namespace. This means that if a cluster administrator runs a TCP service on a node that listens on 127.0.0.1:1234, other hosts on the same LAN or containers on the same node could potentially reach this service. The vulnerability arises when services assume that only localhost processes can access them, leading to potential unauthorized access and attacks.
How To Fix
Latest published version: v1.37.1 as of 23 Oct 2026
go get k8s.io/kubernetes@v1.37.1Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 1.16.111.16.11go get k8s.io/kubernetes@v1.16.11 -
>= 1.17.0, < 1.17.71.17.7go get k8s.io/kubernetes@v1.17.7 -
>= 1.18.0, < 1.18.41.18.4go get k8s.io/kubernetes@v1.18.4
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
As a workaround, cluster administrators can modify the affected services to bind to specific IP addresses other than 127.0.0.1. By using IP addresses that are not accessible to adjacent hosts or containers, the vulnerability can be mitigated. However, this workaround may require changes to the affected services and careful consideration of network configurations.
Conclusion
The discovered vulnerability in Kubernetes allows adjacent hosts or containers to potentially access TCP and UDP services bound to 127.0.0.1, leading to unauthorized access and potential attacks. It is crucial to upgrade to the fixed versions of Kubernetes or apply the recommended workaround to mitigate this vulnerability. For further support on vulnerability remediation, please contact DevNack.com.
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FAQ
Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications.
The Kubelet and kube-proxy components of Kubernetes are affected by this vulnerability.
The vulnerability allows adjacent hosts or containers to potentially access TCP and UDP services bound to 127.0.0.1, leading to unauthorized access and potential attacks.
To fix this vulnerability, it is recommended to upgrade to the fixed versions of Kubernetes as mentioned in the 'how_to_fix' section.
Yes, a workaround is to modify the affected services to bind to IP addresses other than 127.0.0.1 that are not accessible to adjacent hosts or containers.
References
Related vulnerabilities
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