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HighElastic detection rulesElastic

GKE Certificate Signing Request API Client Signer Requested

Detects creation of a GKE CertificateSigningRequest (CSR) that requests the kubernetes.io/kube-apiserver-client signer. This signer issues general API client certificates with few subject restrictions, unlike the…

Description

Detects creation of a GKE CertificateSigningRequest (CSR) that requests the kubernetes.io/kube-apiserver-client signer. This signer issues general API client certificates with few subject restrictions, unlike the restricted kubelet signers used for node certificate rotation. Attackers with CSR permissions use this signer to mint long-lived credentials for privileged identities such as system:kube-controller-manager, enabling persistence and privilege escalation that survives token revocation and RBAC changes.

Detection logic

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Detection requirements

Platform
ContainersESXiIaaSIdentity ProviderLinuxmacOSNetwork DevicesOffice SuiteSaaSWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
event_index

Known benign triggers

  • Custom PKI or administrative tooling may legitimately request kubernetes.io/kube-apiserver-client certificates in self-managed clusters. Baseline approved operators and tune exclusions for known automation on GKE.

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