This CKS practice question tests your understanding of system hardening. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which Linux capability should be dropped to prevent a container from gaining new privileges via setuid binaries?
CAP_NET_RAW
Why wrong: CAP_NET_RAW allows raw sockets, not related to privilege escalation via setuid.
CAP_DAC_OVERRIDE
Why wrong: CAP_DAC_OVERRIDE allows bypassing file permission checks, not directly related to setuid.
CAP_SETUID
CAP_SETUID allows changing user ID, which is required for setuid binaries to function.
CAP_SYS_ADMIN
Why wrong: CAP_SYS_ADMIN is a broad capability, but not specifically for setuid.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
CAP_SETUID
CAP_SETUID (option C) is the Linux capability that controls whether a process can make arbitrary changes to process UIDs (setuid/setgid). Dropping this capability prevents a container from using setuid binaries (e.g., `su`, `sudo`) to escalate privileges, because the kernel will deny any attempt to change the effective UID. This directly addresses the requirement to prevent gaining new privileges via setuid binaries.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
CAP_NET_RAW
Why it's wrong here
CAP_NET_RAW allows raw sockets, not related to privilege escalation via setuid.
CAP_DAC_OVERRIDE
Why it's wrong here
CAP_DAC_OVERRIDE allows bypassing file permission checks, not directly related to setuid.
CAP_SETUID
Why this is correct
CAP_SETUID allows changing user ID, which is required for setuid binaries to function.
Related concept
Read the scenario before looking for a memorised answer.
CAP_SYS_ADMIN
Why it's wrong here
CAP_SYS_ADMIN is a broad capability, but not specifically for setuid.
Common exam traps
CNCF often tests the distinction between capabilities that control privilege escalation (CAP_SETUID) versus those that grant broad system access (CAP_SYS_ADMIN) or file permission bypass (CAP_DAC_OVERRIDE), leading candidates to pick the more familiar but incorrect option.
Detailed technical explanation
Under the hood, when a process executes a setuid binary, the kernel checks if the process has CAP_SETUID in its effective set before allowing the UID change. If CAP_SETUID is dropped, the kernel returns EPERM on the `execve()` call for setuid binaries, effectively preventing privilege escalation. In a real-world scenario, a container with CAP_SETUID retained could run a binary like `su` or a custom setuid-root helper to gain root access, even if the container runs as a non-root user initially.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
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FAQ
System Hardening — This question tests System Hardening — Read the scenario before looking for a memorised answer..
The correct answer is: CAP_SETUID — CAP_SETUID (option C) is the Linux capability that controls whether a process can make arbitrary changes to process UIDs (setuid/setgid). Dropping this capability prevents a container from using setuid binaries (e.g., `su`, `sudo`) to escalate privileges, because the kernel will deny any attempt to change the effective UID. This directly addresses the requirement to prevent gaining new privileges via setuid binaries.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CKS practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKS exam.
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