A security issue was discovered in kube-apiserver before version 1.21.1 where a user may be able to redirect pod traffic to private networks on a node. Kubernetes already prevents creation of Endpoint IPs in the localhost or link-local range, but the same validation was not performed on EndpointSlice IPs.
|09 Jun 2021||ASA-202106-29||AVG-1970||kube-apiserver||Low||insufficient validation|
Workaround ========== To mitigate this vulnerability without upgrading kube-apiserver, you can create a validating admission webhook that prevents EndpointSlices with endpoint addresses in the 127.0.0.0/8 and 169.254.0.0/16 ranges. If you have an existing admission policy mechanism (like OPA Gatekeeper) you can create a policy that enforces this restriction.