The answer is that the user’s IAM policy does not specify the resource ARN of the role. When troubleshooting cross-account IAM role assumption, the key technical concept is that an IAM policy granting sts:AssumeRole must explicitly include the full Amazon Resource Name (ARN) of the target role in the Resource element; without it, the API call fails with an “Access denied” error even if the trust policy on the target role allows the user’s account. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how resource-level permissions interact with trust policies—a common trap is assuming the trust policy alone is sufficient, or confusing the need for an external ID or MFA. Remember the memory tip: “Trust lets you in, but your own policy must name the ARN.”
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. 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 security engineer is troubleshooting an issue where an IAM user cannot assume a role in another AWS account. The trust policy of the role allows the user's account to assume the role, and the user has a policy that allows sts:AssumeRole. The user receives an error: 'Access denied: User is not authorized to perform sts:AssumeRole.' What 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 user's policy does not specify the resource ARN of the role.
Option C is correct because if the user's IAM policy does not explicitly allow the specific role ARN, sts:AssumeRole will fail. Option A is wrong because external ID is optional unless required by the trust policy. Option B is wrong because MFA is not required unless the policy specifies it. Option D is wrong because the trust policy already allows the account.
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 user's policy does not specify the resource ARN of the role.
Why this is correct
The policy must have a Resource element matching the role ARN.
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 role requires an external ID that the user did not provide.
Why it's wrong here
External ID is optional unless the trust policy requires it.
✗
The user must use multi-factor authentication (MFA).
Why it's wrong here
MFA is not required unless the policy specifies it.
✗
The trust policy does not include the user's IAM user ARN.
Why it's wrong here
Trust policy can allow the entire account.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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 user's policy does not specify the resource ARN of the role. — Option C is correct because if the user's IAM policy does not explicitly allow the specific role ARN, sts:AssumeRole will fail. Option A is wrong because external ID is optional unless required by the trust policy. Option B is wrong because MFA is not required unless the policy specifies it. Option D is wrong because the trust policy already allows the account.
What should I do if I get this SCS-C02 question wrong?
Identify which SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company uses IAM roles for EC2 instances. An application running on an EC2 instance needs to read from an S3 bucket in another AWS account. What is the most secure way to grant access?
medium
✓ A.Create an IAM role in the target account with read access to the bucket, and allow the EC2 instance's role to assume it.
B.Store the other account's IAM user access keys in the EC2 instance.
C.Make the bucket public.
D.Create a bucket policy that allows access from the EC2 instance's public IP.
Why A: Option B is correct because using a cross-account IAM role in the target account allows the EC2 instance to assume the role and access the bucket securely, without sharing long-term credentials. Option A is less secure and requires managing keys. Option C is not secure. Option D is overly permissive.
Last reviewed: Jun 20, 2026
Question Discussion
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This SCS-C02 practice question is part of Courseiva's free Amazon Web Services 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 SCS-C02 exam.
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