# 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. - **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`) - **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:** Yes - **Published:** 23 Jul 2020 - **Updated:** 17 Sep 2024 - **Also known as:** DEBIAN-CVE-2020-8557, GHSA-55qj-gj3x-jq9r, GO-2024-2753, RHSA-2021:3915, SUSE-RU-2020:2204-1 ## 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 (Uncontrolled Resource Consumption) ## 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 | Ecosystem | 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 | | `k8s.io/kubernetes` | Go | From 1.1.0 | 1.16.13, 1.17.9, 1.18.6 | | `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: 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. ## 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](https://insights.sbomify.com/CVE-2018-1002105/): Privilege Escalation in Kubernetes (critical 9.8) - [CVE-2017-1000056](https://insights.sbomify.com/CVE-2017-1000056/): Kubernetes Privilege Escalation (critical 9.8) - [CVE-2016-1906](https://insights.sbomify.com/CVE-2016-1906/): Authorization bypass in Openshift (critical 9.8) - [CVE-2023-3676](https://insights.sbomify.com/CVE-2023-3676/): Kubernetes - Windows nodes - Insufficient input sanitization leads to privilege escalation (high 8.8) - [CVE-2023-3955](https://insights.sbomify.com/CVE-2023-3955/): Kubernetes - Windows nodes - Insufficient input sanitization leads to privilege escalation (high 8.8) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2020-8557 and fix it if it is affected. What it is: 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. Exploitation: There is no known exploitation of CVE-2020-8557 in the wild and no public exploit code. Affected packages and fixed versions: - k8s.io/kubernetes/pkg/kubelet (Go): affected from 1.1.0; fixed in 1.16.13 - k8s.io/kubernetes/pkg/kubelet (Go): affected from 1.1.0; fixed in 1.16.13 - k8s.io/kubernetes/pkg/kubelet (Go): affected from 1.17.0; fixed in 1.17.9 - k8s.io/kubernetes/pkg/kubelet (Go): affected from 1.17.0; fixed in 1.17.9 - k8s.io/kubernetes/pkg/kubelet (Go): affected from 1.18.0; fixed in 1.18.6 - k8s.io/kubernetes/pkg/kubelet (Go): affected from 1.18.0; fixed in 1.18.6 - k8s.io/kubernetes (Go): affected from 1.1.0; fixed in 1.16.13, 1.17.9, 1.18.6 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2020-8557/ (Markdown: https://insights.sbomify.com/CVE-2020-8557/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2020-8557 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-8557 - OSV: https://osv.dev/vulnerability/CVE-2020-8557 --- From sbomify Insights: https://insights.sbomify.com/CVE-2020-8557/ Summaries are generated and may contain mistakes; the official description above is the record.