The correct answer is that the system clocks on the identity provider and service provider are significantly out of sync, as this directly causes a SAML assertion validation failure due to clock skew. SAML 2.0 assertions rely on precise timestamps—specifically the NotBefore and NotOnOrAfter conditions—to define a validity window; if the clocks on the IdP and SP differ by more than the allowed tolerance (typically five minutes), the SP will reject the assertion as either expired or not yet valid, even though the IdP logged a successful authentication. On the CISSP exam, this scenario tests your understanding of federated identity management and the operational risks of distributed authentication systems, often appearing as a trap where candidates blame certificate issues or network latency instead. A common memory tip is to think of the "time trust" between domains: if the clocks disagree, the SAML handshake breaks. Remember the mnemonic "SAML Stops When Clocks Drop" to recall that clock skew is the prime suspect for unexplained assertion failures.
CISSP Identity and Access Management Practice Question
This CISSP practice question tests your understanding of identity and access management. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 multinational corporation deploys a single sign-on (SSO) solution using SAML 2.0 across all subsidiaries. Recently, users in one subsidiary report being unable to access an internal application. The identity provider (IdP) logs show successful authentication, but the service provider (SP) logs indicate assertion validation failures. Which of the following is the MOST likely cause?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The system clocks on the IdP and SP are significantly out of sync
SAML 2.0 relies on timestamps (NotBefore and NotOnOrAfter) within the assertion for validity. If the system clocks on the identity provider (IdP) and service provider (SP) are significantly out of sync, the SP will reject the assertion as expired or not yet valid, even though the IdP logs show successful authentication. This is the most common cause of assertion validation failures in cross-domain SSO deployments.
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 system clocks on the IdP and SP are significantly out of sync
Why this is correct
SAML assertions include timestamps; clock skew leads to validation failure.
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 SP is configured to require a specific SAML attribute not present in the assertion
Why it's wrong here
Missing attribute would cause authorization failure, not assertion validation failure.
✗
The IdP server for the subsidiary is temporarily unreachable
Why it's wrong here
If unreachable, authentication would fail at IdP side.
✗
The SAML certificate used by the SP has expired
Why it's wrong here
Expired certificate would cause failures for all users, not just one subsidiary.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse assertion validation failures (which involve timestamps, signatures, or conditions) with authentication failures (which involve credentials or IdP reachability), leading them to incorrectly select options like IdP unreachability or certificate expiration.
Detailed technical explanation
How to think about this question
SAML 2.0 assertions include a Conditions element with NotBefore and NotOnOrAfter attributes, typically allowing a clock skew of a few minutes (e.g., 5 minutes) as defined in the SP's configuration. When clocks drift beyond this tolerance, the SP treats the assertion as invalid, leading to a 'NotBefore' or 'NotOnOrAfter' validation error. In real-world scenarios, NTP misconfiguration or VM clock drift in cloud environments often causes this issue, requiring administrators to synchronize clocks via NTP or adjust the allowed skew in SP metadata.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Identity and Access Management — This question tests Identity and Access Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The system clocks on the IdP and SP are significantly out of sync — SAML 2.0 relies on timestamps (NotBefore and NotOnOrAfter) within the assertion for validity. If the system clocks on the identity provider (IdP) and service provider (SP) are significantly out of sync, the SP will reject the assertion as expired or not yet valid, even though the IdP logs show successful authentication. This is the most common cause of assertion validation failures in cross-domain SSO deployments.
What should I do if I get this CISSP 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.
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