- A
The website uses Certificate Pinning which causes the browser to reject the firewall's certificate.
Certificate pinning causes the browser to expect a specific certificate hash; even a validly signed certificate from the firewall will be rejected.
- B
The firewall's decryption certificate does not have the correct subject name for the website.
Why wrong: Forward proxy automatically generates certificates with the correct subject name from the original server's certificate.
- C
The firewall's decryption certificate is expired.
Why wrong: No expiration errors are seen in logs, and the error is specifically about trust, not expiration.
- D
The decryption policy is configured to 'no-decrypt' for that traffic.
Why wrong: If set to no-decrypt, traffic would pass through without decryption, and no certificate error would appear.
PCNSE Decryption and SSL Inspection Practice Question
This PCNSE practice question tests your understanding of decryption and ssl inspection. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 network administrator is troubleshooting decryption failures for HTTPS traffic to a financial website. The firewall is configured with SSL Forward Proxy decryption policy that applies to the 'financial-services' URL category. The firewall uses an internal CA certificate to sign generated certificates. Users report a certificate error in their browsers when accessing 'https://www.bankofalice.com'. The error says the certificate is not trusted, even though the internal CA certificate is installed on all client devices. The administrator checks the firewall logs and sees no decryption errors; the session is being decrypted successfully. The administrator also confirms that the decryption policy is active and the firewall is not bypassing decryption. What is the most likely cause of the certificate error?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The website uses Certificate Pinning which causes the browser to reject the firewall's certificate.
Option A is correct because certificate pinning (HTTP Public Key Pinning or HPKP) causes the browser to reject any certificate that does not match the pinned public key, even if the firewall's certificate is signed by a trusted internal CA. Since the firewall generates a new certificate on-the-fly with its own key pair, the browser detects the mismatch and displays a certificate error, despite successful decryption at the firewall.
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 website uses Certificate Pinning which causes the browser to reject the firewall's certificate.
Why this is correct
Certificate pinning causes the browser to expect a specific certificate hash; even a validly signed certificate from the firewall will be rejected.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The firewall's decryption certificate does not have the correct subject name for the website.
Why it's wrong here
Forward proxy automatically generates certificates with the correct subject name from the original server's certificate.
- ✗
The firewall's decryption certificate is expired.
Why it's wrong here
No expiration errors are seen in logs, and the error is specifically about trust, not expiration.
- ✗
The decryption policy is configured to 'no-decrypt' for that traffic.
Why it's wrong here
If set to no-decrypt, traffic would pass through without decryption, and no certificate error would appear.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a certificate error means a CA trust issue or expired certificate, but the key clue is that the internal CA is installed and decryption succeeds—pointing to a pinning or key mismatch scenario that bypasses normal certificate validation.
Detailed technical explanation
How to think about this question
Certificate pinning works by embedding a hash of the server's public key or certificate in the HTTP response header (Public-Key-Pins) or via preloaded pin sets in browsers. When the firewall performs SSL forward proxy, it terminates the client connection and re-encrypts with its own certificate, which has a different public key than the original server's pinned key. This causes the browser to reject the connection with a NET::ERR_SSL_PINNED_KEY_NOT_IN_CERT_CHAIN error, even though the CA is trusted. In modern browsers, HPKP is deprecated in favor of Certificate Transparency (CT) expectations, but some financial sites may still use pinning via preloaded lists or Expect-CT headers.
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 practitioner preparing for the PCNSE exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this PCNSE question test?
Decryption and SSL Inspection — This question tests Decryption and SSL Inspection — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The website uses Certificate Pinning which causes the browser to reject the firewall's certificate. — Option A is correct because certificate pinning (HTTP Public Key Pinning or HPKP) causes the browser to reject any certificate that does not match the pinned public key, even if the firewall's certificate is signed by a trusted internal CA. Since the firewall generates a new certificate on-the-fly with its own key pair, the browser detects the mismatch and displays a certificate error, despite successful decryption at the firewall.
What should I do if I get this PCNSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 25, 2026
This PCNSE practice question is part of Courseiva's free Palo Alto Networks 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 PCNSE exam.
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