GKE Certificate Signing Request API Client Signer Requested

Last updated 12 days ago on 2026-07-10

Created 12 days ago on 2026-07-10

About

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.

Tags

Domain: CloudDomain: KubernetesData Source: GCPData Source: GCP Audit LogsData Source: Google Cloud PlatformUse Case: Threat DetectionTactic: PersistenceTactic: Privilege EscalationLanguage: kuery

Severity

high

Risk Score

MITRE ATT&CK™

Privilege Escalation (TA0004)(external, opens in a new tab or window)

↳ Account Manipulation (T1098)(external, opens in a new tab or window)

Persistence (TA0003)(external, opens in a new tab or window)

↳ Account Manipulation (T1098)(external, opens in a new tab or window)

False Positive Examples

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.

License

Elastic License v2(external, opens in a new tab or window)

Definition

Rule Type: Query (Kibana Query Language)
Integration Pack: Prebuilt Security Detection Rules
Index Patterns: logs-gcp.audit-*
Related Integrations: gcp(external, opens in a new tab or window)
Query

✄𐘗text code block:
✄𐘗data_stream.dataset:"gcp.audit" and service.name:"k8s.io" and event.outcome:"success" and
event.action:"io.k8s.certificates.v1.certificatesigningrequests.create" and
gcp.audit.request.spec.signerName:"kubernetes.io/kube-apiserver-client" and
not client.user.email:(
  "system:gcp-controller-manager" or
  "system:serviceaccount:kube-system:certificate-controller"
)

Install detection rules in Elastic Security

Detect GKE Certificate Signing Request API Client Signer Requested in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).