Security Bulletin: IBM Cloud Kubernetes Service is affected by a Kubernetes kubelet and kube-proxy security vulnerability (CVE-2020-8558)

Summary

IBM Cloud Kubernetes Service is affected by a security vulnerability in the Kubernetes kubelet and kube-proxy that could allow neighboring nodes to bypass localhost boundary (CVE-2020-8558)

Vulnerability Details

CVEID: CVE-2020-8558
Description: Kubernetes kube-proxy could allow a remote attacker to bypass security restrictions, caused by a default insecure port setting. By sending a specially-crafted request, an attacker could exploit this vulnerability to gain access to TCP and UDP services on the node(s) which are bound to 127.0.0.1.
CVSS Base Score: 5.4
CVSS Temporal Score: <https://exchange.xforce.ibmcloud.com/vulnerabilities/184769&gt; for more information
CVSS Vector: (CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N)

Affected Products and Versions

IBM Cloud Kubernetes Service 1.18.0-1.18.3
IBM Cloud Kubernetes Service 1.17.0-1.17.6
IBM Cloud Kubernetes Service 1.16.0-1.16.10
IBM Cloud Kubernetes Service 1.5-1.15

Remediation/Fixes

Updates for IBM Cloud Kubernetes Service cluster worker nodes at versions 1.16 and later are available that fix this vulnerability. Customers must update worker nodes created before the fix was available to address the vulnerability. See updating worker nodes for details on updating worker nodes. To verify your cluster worker nodes have been updated, use the following IBM Cloud CLI command to confirm the currently running versions:

ibmcloud ks workers --cluster <cluster name or ID>

If the versions are at one of the following patch levels or later, the cluster worker nodes have the fix:

1.18.4
1.17.7
1.16.11

Customers running IBM Cloud Kubernetes Service clusters at version 1.14 or 1.15 must upgrade to version 1.16. Please review the documentation before starting an upgrade since additional actions may be required.

Customers running IBM Cloud Kubernetes Service clusters at version 1.13 or earlier must create a new cluster and deploy their apps to the new cluster.

IBM Cloud Kubernetes Service versions 1.14 and earlier are no longer supported, and version 1.15 is deprecated. See the IBM Cloud Kubernetes Service Version information and update actions documentation for more information about Kubernetes versions and version support policies.

Workarounds and Mitigations

IBM Cloud Kubernetes Service partially mitigates this vulnerability by disabling the Kubernetes API Server insecure port. You can also partially mitigate this vulnerability by isolating your cluster from other systems on the private network by applying Calico private network policies.

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References

Complete CVSS v3 Guide
On-line Calculator v3

Off

Kubernetes Security Announcement for CVE-2020-8558

Related Information

IBM Secure Engineering Web Portal
IBM Product Security Incident Response Blog

*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.

Disclaimer

Review the IBM security bulletin disclaimer and definitions regarding your responsibilities for assessing potential impact of security vulnerabilities to your environment.

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