AKS | Azure Kubernetes Service: Privilege escalation from compromised node to cluster (CVE-2020-8559)

Hi,

In this article I would like share with you a new vulnerability against Azure Kubernetes.

Title: Privilege escalation from compromised node to cluster

CVE: CVE-2020-8559

Description:

If an attacker is able to intercept certain requests to the Kubelet within Azure Kubernetes Service (AKS), they can send a redirect response that may be followed by a client using the credentials from the original request. This can lead to compromise of other nodes.

If multiple clusters share the same certificate authority trusted by the client, and the same authentication credentials, this vulnerability may allow an attacker to redirect the client to another cluster. In this configuration, this vulnerability should be considered High severity.

Note that this vulnerability requires an attacker to first compromise a node through separate means.

Affected versions:

AKS patches all GA kubernetes versions control plane components automatically.

  • kube-apiserver <v1.18.6
  • kube-apiserver <v1.17.7
  • kube-apiserver <v1.16.10
  • and all kube-apiserver versions prior to v1.15.11

Fixed versions:

  • kube-apiserver v1.18.6+
  • kube-apiserver v1.17.7+
  • kube-apiserver v1.16.10+

Maxime.

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