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Amazon S3 AccessDenied — Troubleshooting Guide

A practical path for diagnosing S3 AccessDenied errors across identity, bucket policy, encryption, and ownership controls.

1 min readLevel: IntermediateUpdated 2026-08-09Review recommended

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troubleshooting AWS S3 IAM security

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Troubleshooting

Start with the symptom. End with a verified fix.

What’s wrong?

An application or user receives AccessDenied while reading, writing, or listing an S3 resource.

Possible causes

Missing identity permission
restrictive bucket policy
explicit deny
KMS permission issue
object ownership or resource mismatch

Diagnosis

Identify the caller
identify the exact S3 action and resource
inspect identity and bucket policies
look for explicit denies
inspect encryption and ownership requirements

2 · Fix

Grant only the missing permission at the narrowest required scope or remove the confirmed conflicting control.

Verify

Repeat the exact operation and confirm CloudTrail or application evidence where available.

3 · Prevent

Use least privilege, policy tests, clear ownership rules, and documented encryption requirements.

Amazon S3 AccessDenied

Start with who is calling, what action is being attempted, and which resource is affected.

Diagnose

Identify the IAM principal or workload role.
Identify the exact action: GetObject, PutObject, ListBucket, and so on.
Confirm the object/bucket ARN is the one your policy actually targets.
Inspect identity policies and bucket policies for both allows and explicit denies.
If SSE-KMS is involved, verify the caller can use the required KMS key.
Check ownership and cross-account requirements.

Fix → Verify → Prevent

Avoid * permissions as a shortcut. Make the smallest policy change that explains the evidence, repeat the failed operation, and retain a policy test or runbook entry for future incidents.

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