This CAS-004 practice question tests your understanding of application environment, configuration and security. 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.
A security engineer is reviewing a CI/CD pipeline that builds a Docker image. The engineer notices that the Dockerfile uses a base image from a public registry, installs packages via apt-get without version pinning, and copies a private SSH key into the image. Which of the following vulnerabilities is MOST directly introduced by this practice?
Use of untrusted base image
Why wrong: While a risk, it's not as directly exploitable as an exposed private key.
Privilege escalation via SUID binaries
Why wrong: No indication of SUID; the main issue is secret leakage.
Dependency confusion from unpinned packages
Why wrong: Unpinned packages are a supply chain risk but not as immediate as credential exposure.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Exposure of sensitive credentials in the image layers
Copying a private SSH key into a Docker image embeds the credential in one of the image's layers. Even if the key is deleted in a later layer, it remains accessible via `docker history` or by pulling the intermediate layers, directly exposing sensitive credentials to anyone who can access the image.
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.
Use of untrusted base image
Why it's wrong here
While a risk, it's not as directly exploitable as an exposed private key.
Privilege escalation via SUID binaries
Why it's wrong here
No indication of SUID; the main issue is secret leakage.
Dependency confusion from unpinned packages
Why it's wrong here
Unpinned packages are a supply chain risk but not as immediate as credential exposure.
Option-by-option analysis
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CAS-004 exam frequently reuses these exact scenarios with slightly different constraints.
Why this is wrong here
While a risk, it's not as directly exploitable as an exposed private key.
Why this is wrong here
No indication of SUID; the main issue is secret leakage.
Why this is wrong here
Unpinned packages are a supply chain risk but not as immediate as credential exposure.
Analysis generated from the official CAS-004blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Cisco often tests the misconception that deleting a file in a later Docker layer removes it from the image, when in fact the underlying layer still contains the sensitive data.
Detailed technical explanation
Docker images are built as layered filesystems; each RUN, COPY, or ADD instruction creates a new layer that persists in the image manifest. Even if a subsequent layer removes the SSH key file, the key data remains in the earlier layer and can be extracted via `docker save` or by inspecting the image history. This is why secrets should never be copied into images; instead, use Docker BuildKit's `--secret` flag or multi-stage builds to avoid embedding credentials.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Application Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Read the scenario before looking for a memorised answer..
The correct answer is: Exposure of sensitive credentials in the image layers — Copying a private SSH key into a Docker image embeds the credential in one of the image's layers. Even if the key is deleted in a later layer, it remains accessible via `docker history` or by pulling the intermediate layers, directly exposing sensitive credentials to anyone who can access the image.
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 11, 2026
This CAS-004 practice question is part of Courseiva's free CompTIA 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 CAS-004 exam.
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