This CKS practice question tests your understanding of cluster setup and hardening. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are auditing RBAC and find a ClusterRoleBinding named 'admin-binding' that binds the 'cluster-admin' ClusterRole to the service account 'default' in namespace 'kube-system'. What is the risk?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Any pod using the default service account in kube-system has cluster-admin privileges
Option C is correct because the ClusterRoleBinding 'admin-binding' binds the 'cluster-admin' ClusterRole to the 'default' service account in the 'kube-system' namespace. Since ClusterRoleBindings are cluster-scoped, they grant permissions across all namespaces. Any pod in the 'kube-system' namespace that uses the 'default' service account (which is the default if no other service account is specified) will inherit cluster-admin privileges, allowing full control over the entire cluster.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The risk is only if the service account is used by external users
Why it's wrong here
Pods in the cluster can use the service account.
✗
The ClusterRoleBinding is invalid because it uses a namespace-scoped service account
Why it's wrong here
Service accounts are namespaced but can be used in ClusterRoleBindings.
✓
Any pod using the default service account in kube-system has cluster-admin privileges
Why this is correct
The service account inherits the cluster-admin role.
Related concept
Read the scenario before looking for a memorised answer.
✗
No risk, as it is limited to kube-system namespace
Why it's wrong here
ClusterRoleBindings are cluster-wide, not limited to a namespace.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between RoleBindings (namespace-scoped) and ClusterRoleBindings (cluster-scoped), and the trap here is that candidates mistakenly think a ClusterRoleBinding to a namespace-scoped service account is invalid or limited to that namespace.
Detailed technical explanation
How to think about this question
Under the hood, a ClusterRoleBinding binds a ClusterRole (which contains non-namespaced resources like nodes and persistent volumes) to subjects, and the binding itself is not namespaced. The 'default' service account in any namespace is automatically mounted into pods unless overridden, so a pod in kube-system using the default service account will have a token that authenticates with the cluster-admin privileges. In a real-world scenario, a compromised pod in kube-system (e.g., a vulnerable kube-proxy or coredns) could leverage this to escalate privileges and control the entire cluster.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
Cluster Setup and Hardening — This question tests Cluster Setup and Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Any pod using the default service account in kube-system has cluster-admin privileges — Option C is correct because the ClusterRoleBinding 'admin-binding' binds the 'cluster-admin' ClusterRole to the 'default' service account in the 'kube-system' namespace. Since ClusterRoleBindings are cluster-scoped, they grant permissions across all namespaces. Any pod in the 'kube-system' namespace that uses the 'default' service account (which is the default if no other service account is specified) will inherit cluster-admin privileges, allowing full control over the entire cluster.
What should I do if I get this CKS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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