mediumMultiple ChoiceObjective-mapped
CAS-004 Practice Question: Refer to the exhibit
Exhibit
access-list 100 permit tcp any any eq 22 access-list 100 permit tcp host 10.0.0.10 any eq 443 access-list 100 permit tcp 192.168.1.0 0.0.0.255 any eq 80 access-list 100 deny ip any any
Refer to the exhibit. A security analyst reviews the following firewall rule on a border firewall. Which vulnerability is present?
⚠ Common exam trap
A common trap is the misconception that an implicit deny rule is missing when the real vulnerability is an overly permissive explicit allow rule, such as SSH from any source, which candidates overlook because they focus on the absence of a deny-all statement.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SSH access is allowed from any source
The firewall rule allows SSH (TCP port 22) from any source, which exposes the border firewall to brute-force attacks, unauthorized access, and potential credential harvesting. SSH should be restricted to specific trusted IP addresses or management networks to reduce the attack surface. An implicit deny rule exists by default at the end of most firewall rule sets, but the explicit permissive SSH rule overrides it, creating a critical security gap.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HTTPS is only allowed from a single host
Why it's wrong here
This is a secure configuration, not a vulnerability.
- ✓
SSH access is allowed from any source
Why this is correct
Permitting SSH from any source exposes the server to unauthorized access attempts.
- ✗
HTTP is allowed from the internal network
Why it's wrong here
This is an intended design for internal users.
- ✗
An implicit deny rule is missing
Why it's wrong here
An explicit deny ip any any is present, so no implicit deny issue.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 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-005 exam.