Quick Answer
The answer is that both the S3 bucket policy or IAM policy and the KMS key policy need changes to resolve the S3 SSE-KMS access denied cross-account error. This is because when an object is encrypted with SSE-KMS, the caller must have explicit s3:GetObject permission from the bucket policy or their IAM role, and the KMS key policy must grant kms:Decrypt to the caller’s AWS account or IAM role; without both, the decryption step fails silently with an AccessDenied even if S3 permissions appear correct. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding that SSE-KMS creates a two-layer permission model—S3 controls object access, while KMS controls key usage—and a common trap is forgetting that cross-account KMS key policies do not trust the caller’s account by default. Remember the memory tip: “S3 for the object, KMS for the key; both must say yes for the download to be free.”
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. 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.
Users receive AccessDenied when downloading SSE-KMS encrypted S3 objects cross-account. Which two policies may need changes?
CloudFront cache policy
Why wrong: This does not meet the stated requirement as directly as the correct option.
S3 bucket/object access policy or IAM policy
Correct for the stated requirement.
KMS key policy allowing decrypt to the caller
Correct for the stated requirement.
Route 53 resolver rule policy
Why wrong: This does not meet the stated requirement as directly as the correct option.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
S3 bucket/object access policy or IAM policy
When accessing SSE-KMS encrypted S3 objects cross-account, the S3 bucket policy or the IAM policy must explicitly grant the s3:GetObject permission to the caller. Additionally, the KMS key policy must allow the kms:Decrypt action for the caller's AWS account or IAM role, because SSE-KMS uses a customer master key (CMK) to encrypt the object, and decryption requires KMS permissions. Without both policies, the request fails with AccessDenied even if the S3 permissions are correct.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
CloudFront cache policy
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
S3 bucket/object access policy or IAM policy
Why this is correct
Correct for the stated requirement.
Related concept
Read the scenario before looking for a memorised answer.
KMS key policy allowing decrypt to the caller
Why this is correct
Correct for the stated requirement.
Related concept
Read the scenario before looking for a memorised answer.
Route 53 resolver rule policy
Why it's wrong here
This does not meet the stated requirement as directly as the correct option.
Common exam traps
The trap here is that candidates often assume only the S3 bucket policy needs updating, forgetting that SSE-KMS adds a second authorization layer via KMS key policies, which must explicitly allow the decrypt action for the cross-account caller.
Detailed technical explanation
Under the hood, SSE-KMS encrypts each S3 object with a unique data key, which is then wrapped by the CMK. When a user downloads the object, S3 calls KMS to decrypt the data key using kms:Decrypt, and the KMS key policy must allow this operation for the caller's principal. A common subtlety is that the KMS key policy must explicitly grant access to the external account or IAM role, and the IAM policy in the external account must also allow kms:Decrypt; a bucket policy alone is insufficient for cross-account access with SSE-KMS.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
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FAQ
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
The correct answer is: S3 bucket/object access policy or IAM policy — When accessing SSE-KMS encrypted S3 objects cross-account, the S3 bucket policy or the IAM policy must explicitly grant the s3:GetObject permission to the caller. Additionally, the KMS key policy must allow the kms:Decrypt action for the caller's AWS account or IAM role, because SSE-KMS uses a customer master key (CMK) to encrypt the object, and decryption requires KMS permissions. Without both policies, the request fails with AccessDenied even if the S3 permissions are correct.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
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 developer receives an Access Denied error when trying to download an object from an S3 bucket. The developer's IAM policy is shown in the exhibit. The bucket policy also grants access. What is the MOST likely cause?
hardWhy B: Option B is correct because if the bucket is encrypted with a KMS key, the user must also have kms:Decrypt permission. Option A is wrong because the policy explicitly allows s3:GetObject. Option C is wrong because the bucket policy also grants access, so it's not a bucket policy issue. Option D is wrong because public access is not required if IAM policies allow access.
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Last reviewed: Jun 11, 2026
This DVA-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 DVA-C02 exam.
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