Quick Answer
The answer is that the S3 bucket policy Deny overrides the IAM role permissions. Even though your EC2 instance has an IAM role with a policy allowing s3:GetObject, an explicit Deny in the bucket policy takes precedence over any Allow, regardless of the principal or source. This is because AWS evaluates all policies (identity-based and resource-based) and an explicit Deny is final—it cannot be overridden by any Allow. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of the policy evaluation logic, specifically the distinction between identity-based and resource-based policies. A common trap is assuming that attaching an IAM role to an EC2 instance is sufficient, but you must always check if the S3 bucket itself has a Deny statement. Memory tip: "Deny is the final word—once it says no, no Allow can say yes."
This SOA-C02 practice question tests your understanding of security and compliance. 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 SysOps administrator is troubleshooting an issue where an EC2 instance cannot access an S3 bucket using an instance profile. The instance profile has an IAM role with a policy that allows s3:GetObject on the bucket. The S3 bucket policy has a Deny for all principals except a specific service role. What is the most likely reason for the access failure?
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.
The IAM role trust policy does not allow EC2 to assume the role.
Why wrong: The trust policy allows EC2.
The instance profile is not correctly attached to the EC2 instance.
Why wrong: The instance profile is attached.
The S3 bucket requires a VPC endpoint.
Why wrong: No such requirement.
The S3 bucket policy Deny overrides the IAM role permissions.
Explicit Deny in bucket policy takes precedence.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The S3 bucket policy Deny overrides the IAM role permissions.
Option C is correct because when a bucket policy explicitly denies access, it overrides any IAM permissions. Option A is wrong because instance profiles can be used with S3. Option B is wrong because S3 does not require a VPC endpoint. Option D is wrong because the Deny in the bucket policy applies regardless of trust policy.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The IAM role trust policy does not allow EC2 to assume the role.
Why it's wrong here
The trust policy allows EC2.
The instance profile is not correctly attached to the EC2 instance.
Why it's wrong here
The instance profile is attached.
The S3 bucket requires a VPC endpoint.
Why it's wrong here
No such requirement.
The S3 bucket policy Deny overrides the IAM role permissions.
Why this is correct
Explicit Deny in bucket policy takes precedence.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
Common exam traps
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
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
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SOA-C02 ACL questions on filtering logic and placement.
Security and Compliance — study guide chapter
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FAQ
Security and Compliance — This question tests Security and Compliance — Standard ACLs match source addresses..
The correct answer is: The S3 bucket policy Deny overrides the IAM role permissions. — Option C is correct because when a bucket policy explicitly denies access, it overrides any IAM permissions. Option A is wrong because instance profiles can be used with S3. Option B is wrong because S3 does not require a VPC endpoint. Option D is wrong because the Deny in the bucket policy applies regardless of trust policy.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SOA-C02 ACL questions on filtering logic and placement.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Standard ACLs match source addresses.
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Last reviewed: Jun 20, 2026
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