Kubetier
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T1

create endpointslices

Writing EndpointSlices sets which IPs kube-proxy treats as Service backends.

In multi-tenant or loosely governed clusters this redirects Service traffic to cloud metadata, node-local services, or attacker-controlled endpoints.

Note:

CVE-2021-25740: architectural confused-deputy risk from Endpoint/EndpointSlice write access, not a version-gated fix.

Default admin/edit roles lost Endpoint/EndpointSlice write in v1.22+, but explicit grants remain dangerous regardless of cluster version.

API Group
discovery.k8s.io
Scope
namespaced
Audit Level
Request

Escalation Paths

  1. Create or modify Endpoints or EndpointSlices so a Service resolves to addresses it was never meant to reach, such as node-local services or an attacker-controlled host.

  2. kube-proxy programs those addresses and every client of that Service follows them.

  3. Callers keep using the Service name they trust, which is what makes the Service the confused deputy.

  4. End-to-end delivery depends on the CNI and kube-proxy mode in use, so the reachable destination set varies by cluster.

Additional rights needed:

none

Note:

CVE-2021-25740 is best treated as a confused-deputy risk from write access to Endpoints/EndpointSlices, not a clean version-gated issue.

Kubernetes removed broad Endpoint/EndpointSlice write from default admin/edit roles in v1.22+, but explicit grants remain dangerous.

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