CVE-2020-8557 Kubernetes node disk Denial of Service by writing to container /etc/hosts
An attacker can cause a Kubernetes node to fail by filling its disk space through excessive writes to the container's /etc/hosts file.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2020-8557?
CVE-2020-8557 is a medium-severity denial of service vulnerability in Kubernetes Kubernetes, published on 23 Jul 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-400
Which versions are affected by CVE-2020-8557?
7 open source packages ship an affected version, including k8s.io/kubernetes/pkg/kubelet and k8s.io/kubernetes. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
k8s.io/kubernetes/pkg/kubelet Go | From 1.1.0 | 1.16.13 |
k8s.io/kubernetes/pkg/kubelet Go | From 1.1.0 | 1.16.13 |
k8s.io/kubernetes/pkg/kubelet Go | From 1.17.0 | 1.17.9 |
k8s.io/kubernetes/pkg/kubelet Go | From 1.17.0 | 1.17.9 |
k8s.io/kubernetes/pkg/kubelet Go | From 1.18.0 | 1.18.6 |
k8s.io/kubernetes/pkg/kubelet Go | From 1.18.0 | 1.18.6 |
1 more packages
k8s.io/kubernetes Go | From 1.1.0 | 1.16.13, 1.17.9, 1.18.6 |
Linux distribution packages (14)
atomic-openshift Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-clients Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-clients-redistributable Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-docker-excluder Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-excluder Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-hyperkube Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-hypershift Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-master Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-node Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-pod Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-sdn-ovs Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-template-service-broker Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
atomic-openshift-tests Red Hat:openshift:3.11::el7 | All versions | 0:3.11.542-1.git.0.f2fd300.el7 |
kubernetes SUSE:Linux Enterprise Module for Containers 15 SP1 | All versions | 1.17.4-4.18.1 |
Products include Kubernetes Kubernetes.
How do I fix CVE-2020-8557?
Upgrade k8s.io/kubernetes/pkg/kubelet to a fixed version for your release line: 1.16.13, 1.17.9 or 1.18.6.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2020-8557 being exploited?
There is no known exploitation of CVE-2020-8557 in the wild and no public exploit code.
Other vulnerabilities in Kubernetes Kubernetes
- CVE-2018-1002105 Privilege Escalation in Kubernetes
- CVE-2017-1000056 Kubernetes Privilege Escalation
- CVE-2016-1906 Authorization bypass in Openshift
- CVE-2023-3676 Kubernetes - Windows nodes - Insufficient input sanitization leads to privilege escalation
- CVE-2023-3955 Kubernetes - Windows nodes - Insufficient input sanitization leads to privilege escalation
Sources
Also known as DEBIAN-CVE-2020-8557, GHSA-55qj-gj3x-jq9r, GO-2024-2753, RHSA-2021:3915, SUSE-RU-2020:2204-1.