A security issue was discovered in kube-apiserver that could allow node updates to bypass a Validating Admission Webhook. Clusters are only affected by this vulnerability if they run a Validating Admission Webhook for Nodes that denies admission based at least partially on the old state of the Node object. Validating Admission Webhook does not observe some previous fields.

Kube-proxy on Windows can unintentionally forward traffic to local processes listening on the same port (“spec.ports[].port”) as a LoadBalancer Service when the LoadBalancer controller does not set the “status.loadBalancer.ingress[].ip” field. Clusters where the LoadBalancer controller sets the “status.loadBalancer.ingress[].ip” field are unaffected.

A flaw was found in kubernetes. In Kubernetes, if the logging level is to at least 4, processing a malformed docker config file will result in the contents of the docker config file being leaked, which can include pull secrets or other registry credentials. This can occur with client tools like kubectl, or other components that use registry credentials in a docker config file.

A flaw was found in kubernetes. In Kubernetes, if the logging level is to at least 9, authorization and bearer tokens will be written to log files. This can occur both in API server logs and client tool output like kubectl. Previously, CVE-2019-11250 was assigned for the same issue for logging levels of at least 4.

A flaw was found in kubernetes. If the logging level is to at least 4, and Ceph RBD is configured as a storage provisioner, then Ceph RBD admin secrets can be written to logs. This occurs in kube-controller-manager's logs during provisioning of Ceph RBD persistent claims.

A security issue was discovered in Kubernetes where a user may be able to redirect pod traffic to private networks on a Node. Kubernetes already prevents creation of Endpoint IPs in the localhost or link-local range, but the same validation was not performed on EndpointSlice IPs.

As mitigations to a report from 2019 and CVE-2020-8555, Kubernetes attempts to prevent proxied connections from accessing link-local or localhost networks when making user-driven connections to Services, Pods, Nodes, or StorageClass service providers. As part of this mitigation Kubernetes does a DNS name resolution check and validates that response IPs are not in the link-local (169.254.0.0/16) or localhost (127.0.0.0/8) range. Kubernetes then performs a second DNS resolution without validation for the actual connection. If a non-standard DNS server returns different non-cached responses, a user may be able to bypass the proxy IP restriction and access private networks on the control plane.