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.
Metrics
CVSS Version: 3.1 |
Base Score: 2.2 LOW Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N
l➤ Exploitability Metrics: Attack Vector (AV)* NETWORK Attack Complexity (AC)* HIGH Privileges Required (PR)* HIGH User Interaction (UI)* NONE Scope (S)* UNCHANGED