CVE-2020-8554

Kubernetes man in the middle using LoadBalancer or ExternalIPs

Published Jan 21, 2021 CVSS 3.1 · 6.3 Medium EPSS 8.7% KEV · Not listed
Description
Kubernetes API server in all versions allow an attacker who is able to create a ClusterIP service and set the spec.externalIPs field, to intercept traffic to that IP address. Additionally, an attacker who is able to patch the status (which is considered a privileged operation and should not typically be granted to users) of a LoadBalancer service can set the status.loadBalancer.ingress.ip to similar effect.

Remediation

Vendor Workaround

To restrict the use of external IPs we are providing an admission webhook container: k8s.gcr.io/multitenancy/externalip-webhook:v1.0.0. The source code and deployment instructions are published at https://github.com/kubernetes-sigs/externalip-webhook. Alternatively, external IPs can be restricted using OPA Gatekeeper. A sample ConstraintTemplate and Constraint can be found here: https://github.com/open-policy-agent/gatekeeper-library/tree/master/library/general/externalip.

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-j9wf-vvm6-4r9w Unverified Ownership in Kubernetes