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Kubernetes Client Certificate Signing Request Created or Approved

Detects creation or approval of a Kubernetes CertificateSigningRequest (CSR) by a non-system identity. Attackers who have gained cluster access can submit a CSR with a privileged Common Name such as…

Description

Detects creation or approval of a Kubernetes CertificateSigningRequest (CSR) by a non-system identity. Attackers who have gained cluster access can submit a CSR with a privileged Common Name such as system:kube-controller-manager or system:masters, then approve it themselves to obtain a long-lived client certificate. Unlike service account tokens which expire in hours, client certificates persist until they expire or the cluster CA is rotated, providing durable access that survives pod termination, token revocation, and RBAC changes. On non-EKS clusters, the signed certificate allows the attacker to authenticate as the privileged identity from anywhere without needing cluster network access, making it one of the most persistent backdoor mechanisms available in Kubernetes.

Detection logic

Its licence does not clear it for publishing here

Sunturai publishes a detection's own text where the licence it arrived under has been reviewed and permits it, and Elastic License 2.0 has not. The query as its source wrote it, its canonical form and the hash that pins this revision are in the workspace record.

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

  • Approved certificate workflows (for example cert-manager, internal PKI rotation, or node bootstrap) may create or update CSRs from identities not in the exclusion list if they run under a custom service account. Baseline automation that legitimately approves CSRs and tune exclusions for those principals.

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