Security Bulletin: IBM Cloud Kubernetes Service is affected by a Denial of Service vulnerability in Kubernetes API server

Summary

IBM Cloud Kubernetes Service is affected by a security vulnerability in Kubernetes which could cause a Denial of Service on the API Server.

Vulnerability Details

CVEID: CVE-2019-1002100 DESCRIPTION: Users that are authorized to make patch requests to the Kubernetes API Server can send a specially crafted patch of type “json-patch” (e.g. kubectl patch --type json or "Content-Type: application/json-patch+json") that consumes excessive resources while processing, causing a Denial of Service on the API Server.
CVSS Base Score: 6.5
CVSS Temporal Score:
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

Affected Products and Versions

IBM Cloud Kubernetes Service 1.13.0-1.13.3
IBM Cloud Kubernetes Service 1.12.0-1.12.5
IBM Cloud Kubernetes Service 1.11.0-1.11.7
IBM Cloud Kubernetes Service 1.10.0-1.10.13
IBM Cloud Kubernetes Service 1.5-1.9

Remediation/Fixes

IBM Cloud Kubernetes Service clusters at versions 1.11 and later have been updated to address this vulnerability. If your clusters are at versions 1.11, 1.12 or 1.13 there is no need to update worker nodes to address this vulnerability.

In some situations IBM Cloud Kubernetes Service might not have been able to update a cluster. To verify your clusters are no longer exposed use the following IBM Cloud CLI command to confirm the currently running versions:

ibmcloud ks clusters

If your versions are at one of the following levels or later, you are no longer exposed to this vulnerability:

1.11.8
1.12.6
1.13.4

If one or more of your clusters is at version 1.11, 1.12 or 1.13 and has not been automatically updated then use the following IBM Cloud CLI command to complete the update, replacing “1.##” with the target version:

ibmcloud ks cluster-update --cluster <cluster-name> --kube-version 1.##

Customers running IBM Cloud Kubernetes Service clusters at version 1.10 must upgrade their affected clusters to version 1.11 or 1.12. Customers running IBM Cloud Kubernetes Service clusters at version 1.7, 1.8 or 1.9 must upgrade first to version 1.10 and then to version 1.11 or 1.12. To upgrade a cluster use the following IBM Cloud CLI command, replacing “1.##” with the target version. Please review the documentation before starting the upgrade since additional actions may be required.

ibmcloud ks cluster-update --cluster <cluster-name> --kube-version 1.##

If you are running a version of IBM Cloud Kubernetes Service 1.5 there is no migration path.

Note: IBM Cloud Kubernetes Service versions 1.5, 1.7, 1.8 and 1.9 are no longer supported. 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

Remove ‘patch’ permissions from untrusted users.