kubernetes vulnerabilities · Page 2

Node address isn't always verified when proxying

Users may have access to secure endpoints in the control plane network. Kubernetes clusters are only affected if an untrusted user can modify Node objects and send proxy requests to them. Kubernetes supports node proxying, which allows clients of kube-apiserver to access endpoints of a Kubelet to establish connections to Pods, retrieve container logs, and more. While Kubernetes already validates the proxying address for Nodes, a bug in kube-apiserver made it possible to bypass this validation. Bypassing this validation could allow authenticated requests destined for Nodes to to the API server's private network.

Unauthorized read of Custom Resources

Users authorized to list or watch one type of namespaced custom resource cluster-wide can read custom resources of a different type in the same API group without authorization. Clusters are impacted by this vulnerability if all of the following are true: 1. There are 2+ CustomResourceDefinitions sharing the same API group 2. Users have cluster-wide list or watch authorization on one of those custom resources. 3. The same users are not authorized to read another custom resource in the same API group.

Bypass of Kubernetes API Server proxy TOCTOU

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

ANSI escape characters in kubectl output are not being filtered

kubectl does not neutralize escape, meta or control sequences contained in the raw data it outputs to a terminal. This includes but is not limited to the unstructured string fields in objects such as Events.

Symlink Exchange Can Allow Host Filesystem Access

A security issue was discovered in Kubernetes where a user may be able to create a container with subpath volume mounts to access files & directories outside of the volume, including on the host filesystem.

Holes in EndpointSlice Validation Enable Host Network Hijack

A security issue was discovered with Kubernetes that could enable users to send network traffic to locations they would otherwise not have access to via a confused deputy attack.

Webhook redirect in kube-apiserver

A security issue was discovered in Kubernetes where actors that control the responses of MutatingWebhookConfiguration or ValidatingWebhookConfiguration requests are able to redirect kube-apiserver requests to private networks of the apiserver. If that user can view kube-apiserver logs when the log level is set to 10, they can view the redirected responses and headers in the logs.

Holes in EndpointSlice Validation Enable Host Network Hijack

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.

Validating Admission Webhook does not observe some previous fields

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.

Kubernetes man in the middle using LoadBalancer or ExternalIPs

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.

Secret leaks in logs for vSphere Provider kube-controller-manager

In Kubernetes clusters using VSphere as a cloud provider, with a logging level set to 4 or above, VSphere cloud credentials will be leaked in the cloud controller manager's log. This affects < v1.19.3.

Docker config secrets leaked when file is malformed and loglevel >= 4

In Kubernetes clusters using a logging level of 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 affects < v1.19.3, < v1.18.10, < v1.17.13.

Incomplete fix for CVE-2019-11250 allows for token leak in logs when logLevel >= 9

In Kubernetes, if the logging level is set 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. This affects <= v1.19.3, <= v1.18.10, <= v1.17.13, < v1.20.0-alpha2.

Ceph RBD adminSecrets exposed in logs when loglevel >= 4

In Kubernetes clusters using Ceph RBD as a storage provisioner, with logging level of at least 4, Ceph RBD admin secrets can be written to logs. This occurs in kube-controller-manager's logs during provisioning of Ceph RBD persistent claims. This affects < v1.19.3, < v1.18.10, < v1.17.13.

Kubernetes node setting allows for neighboring hosts to bypass localhost boundary

The Kubelet and kube-proxy components in versions 1.1.0-1.16.10, 1.17.0-1.17.6, and 1.18.0-1.18.3 were found to contain a security issue which allows adjacent hosts to reach TCP and UDP services bound to 127.0.0.1 running on the node or in the node's network namespace. Such a service is generally thought to be reachable only by other processes on the same host, but due to this defeect, could be reachable by other hosts on the same LAN as the node, or by containers running on the same node as the service.

Kubernetes node disk Denial of Service by writing to container /etc/hosts

The Kubernetes kubelet component in versions 1.1-1.16.12, 1.17.0-1.17.8 and 1.18.0-1.18.5 do not account for disk usage by a pod which writes to its own /etc/hosts file. The /etc/hosts file mounted in a pod by kubelet is not included by the kubelet eviction manager when calculating ephemeral storage usage by a pod. If a pod writes a large amount of data to the /etc/hosts file, it could fill the storage space of the node and cause the node to fail.

• Update to 1.16.13
• Update to 1.17.9
• Update to 1.18.6

Credential leakage when failing to mount

The Kubernetes kube-controller-manager in versions v1.0-v1.17 is vulnerable to a credential leakage via error messages in mount failure logs and events for AzureFile and CephFS volumes.

Privilege escalation from compromised node to cluster

The Kubernetes kube-apiserver in versions v1.6-v1.15, and versions prior to v1.16.13, v1.17.9 and v1.18.6 are vulnerable to an unvalidated redirect on proxied upgrade requests that could allow an attacker to escalate privileges from a node compromise to a full cluster compromise.

Kubernetes kube-controller-manager SSRF

The Kubernetes kube-controller-manager in versions v1.0-1.14, versions prior to v1.15.12, v1.16.9, v1.17.5, and version v1.18.0 are vulnerable to a Server Side Request Forgery (SSRF) that allows certain authorized users to leak up to 500 bytes of arbitrary information from unprotected endpoints within the master's host network (such as link-local or loopback services).

• Update to 1.15.12
• Update to 1.16.9
• Update to 1.17.5

Kubernetes API Server denial of service vulnerability from malicious YAML payloads

The Kubernetes API Server component in versions 1.1-1.14, and versions prior to 1.15.10, 1.16.7 and 1.17.3 allows an authorized user who sends malicious YAML payloads to cause the kube-apiserver to consume excessive CPU cycles while parsing YAML.