Quick Answer
The answer is to map port 80 to a non-privileged port and grant the CAP_NET_BIND_SERVICE capability, as this allows the container to bind low ports without requiring full root privileges. This works because Linux capabilities break down root-level permissions into granular units; CAP_NET_BIND_SERVICE specifically permits binding to ports below 1024, while the container process itself runs as a non-root user, minimizing the attack surface. On the CompTIA SecurityX CAS-005 exam, this scenario tests your understanding of the principle of least privilege in container security—a common trap is assuming you must run the container as root or use host networking to bind low ports, both of which weaken isolation. Remember the mnemonic “Cap, Not Root” to recall that capabilities like CAP_NET_BIND_SERVICE solve low port binding without elevating the entire container.
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.
An organization is migrating a legacy application to a containerized environment. The application requires root privileges to bind to a low port (80). What is the most secure approach to handle this requirement?
Map port 80 to a non-privileged port and grant CAP_NET_BIND_SERVICE capability
Allows binding to low port without full root privileges.
Change the application to use a high port (e.g., 8080)
Why wrong: May not be possible without application changes.
Run the container as root and bind to port 80
Why wrong: Running as root violates least privilege principle.
Use host networking mode
Why wrong: Host networking reduces network isolation.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Map port 80 to a non-privileged port and grant CAP_NET_BIND_SERVICE capability
Option D (Use a privileged port mapping and run the container as non-root, granting CAP_NET_BIND_SERVICE capability) is correct because it avoids running the container as root while still allowing binding to low ports. Option A runs as root, insecure. Option B uses host network, reducing isolation. Option C changes port, but may not be feasible.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Map port 80 to a non-privileged port and grant CAP_NET_BIND_SERVICE capability
Why this is correct
Allows binding to low port without full root privileges.
Related concept
Authentication checks who the user is.
Change the application to use a high port (e.g., 8080)
Why it's wrong here
May not be possible without application changes.
Run the container as root and bind to port 80
Why it's wrong here
Running as root violates least privilege principle.
Use host networking mode
Why it's wrong here
Host networking reduces network isolation.
Common exam traps
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CAS-004 questions on access control and AAA configuration.
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FAQ
Application Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Authentication checks who the user is..
The correct answer is: Map port 80 to a non-privileged port and grant CAP_NET_BIND_SERVICE capability — Option D (Use a privileged port mapping and run the container as non-root, granting CAP_NET_BIND_SERVICE capability) is correct because it avoids running the container as root while still allowing binding to low ports. Option A runs as root, insecure. Option B uses host network, reducing isolation. Option C changes port, but may not be feasible.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CAS-004 questions on access control and AAA configuration.
Authentication checks who the user is.
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Last reviewed: Jun 24, 2026
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