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Identity and Access Management →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the bucket policy uses the role ARN in the Principal element instead of the AWS account ID, which is the most likely cause of the failure. This is because S3 bucket policies evaluate the Principal as the identity that makes the request, and when you specify a role ARN, the policy only grants access to that specific role session—not to the users who assume the role. For cross-account access, the Principal must be set to the AWS account ID of the other account, as the role ARN is not a valid principal for S3 bucket policies in the same way an account ID is. On the AWS Certified Security Specialty SCS-C02 exam, this tests your understanding of how S3 bucket policies handle cross-account principals versus IAM role trust policies, which use the role ARN. A common trap is confusing the Principal element in bucket policies with the trust policy of a role. Remember the memory tip: "Bucket policies love accounts, trust policies love roles."

SCS-C02 Identity and Access Management Practice Question

This SCS-C02 practice question tests your understanding of identity and access management. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 company has an S3 bucket policy that allows cross-account access for a specific IAM role in another account. The bucket policy includes a Principal element with the ARN of the role. However, users in the other account that assume the role are unable to access the bucket. 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.

Question 1mediummultiple choice

Full question →

A
The IAM role does not have a permissions policy granting s3:GetObject on the bucket.
Why wrong: While the role needs permissions, the question asks for the most likely cause given the symptom; the Principal error is more fundamental.
B
The bucket policy has an explicit Deny statement that overrides the Allow.
Why wrong: An explicit Deny would block access, but the scenario does not mention one; the likely cause is the incorrect Principal.
C
The role's trust policy does not allow the S3 service to assume the role.
Why wrong: The trust policy controls who can assume the role, not which services the role can access; the role is already assumed by users.
D
The bucket policy uses the role ARN in the Principal element instead of the AWS account ID.
S3 bucket policies require the AWS account ID as Principal for cross-account access; role ARNs are not valid principals.

Full breakdown with real-world context →

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 bucket policy uses the role ARN in the Principal element instead of the AWS account ID.

Option D is correct because when an S3 bucket policy uses a role ARN in the Principal element, the policy only grants access to that specific role session, not to the users who assume the role. Cross-account access via S3 bucket policies requires the Principal to be set to the AWS account ID (or a canonical user ID) of the other account, not the ARN of a role. The role ARN in the Principal element is not evaluated as a valid principal for S3 bucket policies in the same way as an account ID, causing the access to fail.

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 IAM role does not have a permissions policy granting s3:GetObject on the bucket.
Why it's wrong here
While the role needs permissions, the question asks for the most likely cause given the symptom; the Principal error is more fundamental.
✗
The bucket policy has an explicit Deny statement that overrides the Allow.
Why it's wrong here
An explicit Deny would block access, but the scenario does not mention one; the likely cause is the incorrect Principal.
✗
The role's trust policy does not allow the S3 service to assume the role.
Why it's wrong here
The trust policy controls who can assume the role, not which services the role can access; the role is already assumed by users.
✓
The bucket policy uses the role ARN in the Principal element instead of the AWS account ID.
Why this is correct
S3 bucket policies require the AWS account ID as Principal for cross-account access; role ARNs are not valid principals.
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.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume that specifying a role ARN in the Principal element of an S3 bucket policy is sufficient for cross-account access, but AWS requires the Principal to be the account ID for the policy to be evaluated correctly across accounts.

Trap categories for this question

Scenario analysis trap
An explicit Deny would block access, but the scenario does not mention one; the likely cause is the incorrect Principal.

Detailed technical explanation

How to think about this question

In AWS, S3 bucket policies evaluate the Principal element to determine which AWS accounts or IAM entities are allowed or denied access. When a role ARN is used in the Principal, the policy only matches the specific role session, but cross-account access typically requires the Principal to be the AWS account ID (e.g., 'AWS': '123456789012') because S3 bucket policies are evaluated at the account level, not the role level. Additionally, the role's trust policy must allow the users in the other account to assume the role, but that is separate from the bucket policy's Principal configuration.

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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.

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 SCS-C02 question test?

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 bucket policy uses the role ARN in the Principal element instead of the AWS account ID. — Option D is correct because when an S3 bucket policy uses a role ARN in the Principal element, the policy only grants access to that specific role session, not to the users who assume the role. Cross-account access via S3 bucket policies requires the Principal to be set to the AWS account ID (or a canonical user ID) of the other account, not the ARN of a role. The role ARN in the Principal element is not evaluated as a valid principal for S3 bucket policies in the same way as an account ID, causing the access to fail.

What should I do if I get this SCS-C02 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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Same concept, more angles

1 more ways this is tested on SCS-C02

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 wants to grant cross-account access to an S3 bucket. The bucket policy allows access from account 111111111111. An IAM user in account 111111111111 has a policy allowing s3:GetObject on that bucket. However, the user gets AccessDenied. What is the most likely reason?

hard

A.The S3 bucket is in a different region and requires a VPC endpoint.
B.The IAM user policy is attached to a group, not directly to the user.
✓ C.The bucket policy grants access to the account, but the IAM user's ARN is not explicitly listed.
D.The IAM user policy has an explicit deny for s3:GetObject.

Why C: Option A is correct because the S3 bucket policy must explicitly grant access to the IAM user ARN, not just the account. Option B is wrong because explicit deny in the IAM policy would be unusual. Option C is wrong because S3 does not require VPC endpoints. Option D is wrong because the user is in the same account as the policy.

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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.