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GHSA-qh36-44jv-c8xj

Potential proxy IP restriction bypass in Kubernetes

Source: GitHub Advisory Database (reviewed) Low CVE-2020-8562

Packages

EcosystemPackageAffectedFixed in
Go k8s.io/kubernetes >= 1.21.0, <= 1.21.1 no fix listed
Go k8s.io/kubernetes >= 1.20.0, <= 1.20.7 no fix listed
Go k8s.io/kubernetes >= 1.19.0, <= 1.19.11 no fix listed
Go k8s.io/kubernetes <= 1.18.19 no fix listed

Details

As written in the advisory (Markdown source, shown as plain text).

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. All versions of Kubernetes are impacted, and there is no fix in place.

References

External links from the advisory. They lead to third-party sites.