Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteIf your office can access an Amazon S3 bucket but your servers receive 403 Access Denied, the requests may be taking different network paths. A policy condition that permits the office’s public IP can fail to match server traffic routed through an S3 VPC endpoint. That is a plausible cause, not a confirmed diagnosis: the precise denial depends on the policy, caller, operation, and route. Compare a successful office request with a failed server request before changing the policy.
What an S3 403 tells you—and what it does not
An S3 HTTP 403 means the request was denied. The denial can be explicit, such as a policy Deny statement, or implicit because no applicable policy grants the requested access. AWS explains that “An explicit denial occurs when a policy contains a Deny statement for the specific AWS action.” A successful office request does not prove that the server has permission for the same operation or resource. AWS’s S3 403 troubleshooting guide describes these denial types and possible policy layers.
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Start with the exact denied action and resource. For example, s3:GetObject on an object and s3:ListBucket on a bucket are distinct permissions with different resource scopes. A successful console visit, bucket listing, or request for one object is not proof that other operations are authorized.
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Use the failed server request and a successful office request from as close to the same time as practical. Compare the actual request details rather than assuming they share a principal, action, resource, or route.
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- Caller: record the IAM user or role making each request. For a server on EC2, identify the role credentials actually used by the application.
- Action and resource: note the API operation and the bucket or object ARN it targets.
- Request context: record the source IP, timestamp, and whether the request traversed an S3 VPC endpoint.
- Denial details: capture the full error message and any request or extended request IDs returned by S3.
Where available, enhanced access-denied messages can identify the type of policy responsible for a denial. AWS says supported same-account and same-organization requests may include the denial reason; explicit-deny context can also identify the policy ARN. This context is not available for every request relationship or every denial source, and AWS documents limits that include some VPC endpoint policy denials. Check AWS’s guidance on enhanced access-denied messages rather than treating a short or generic 403 as proof of a bucket-policy problem.
Check whether the two requests use different network paths
An office request may reach S3 over the public internet using the office’s public egress IP. A server request may instead travel through an S3 VPC endpoint. Those requests can have different policy context even when they target the same bucket.
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A particularly important condition-key mismatch occurs when a policy relies on aws:SourceIp. AWS states that aws:SourceIp cannot be used in an identity policy or bucket policy for S3 requests traversing a VPC endpoint. If the server uses that route, an office-IP condition is not a suitable way to authorize that request. Review the endpoint-aware condition keys and the actual route described in AWS’s S3 VPC endpoint documentation.
Also inspect the VPC endpoint’s own policy. It must allow the required principal, actions, and bucket resources for requests that pass through it. A bucket policy that appears permissive does not make an endpoint policy irrelevant.
Review every policy layer that can affect the request
A bucket policy is only one part of S3 authorization. Check the workload role’s identity-based IAM policy, the bucket policy, the VPC endpoint policy if applicable, and any AWS Organizations controls. Depending on the bucket and request, other controls—including ACLs, S3 Block Public Access, encryption requirements, Object Lock, access points, or CloudFront—may also be relevant. AWS lists these among potential sources of access failures in its S3 403 troubleshooting guidance.
For a same-account request, the required access must be allowed by applicable policies, and an applicable explicit deny takes precedence. For cross-account access, the relevant policies on both sides must permit the request, with no applicable deny blocking it. Broad permissions on the server role do not override an explicit bucket-policy deny. For the policy evaluation distinctions, see AWS’s IAM policy evaluation logic.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Choose a policy change that matches the intended access
Do not remove a condition or weaken a deny until you know which callers and routes it affects. The right change depends on the bucket’s intended users, network design, actions, and resources. These approaches are not interchangeable:
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| Policy approach | What it targets | What to verify |
|---|---|---|
| Allow a named workload role | A specific IAM principal, with explicitly scoped actions and bucket or object resources. | Confirm the server uses that role, and account for whether cross-account access is involved. |
| Allow office traffic by public egress IP | Requests arriving with the office’s public source IP. | Verify the actual office egress IP and do not rely on this condition for S3 requests through a VPC endpoint. |
| Use endpoint-aware conditions and endpoint policy | Requests following the intended VPC or endpoint path. | Check the request’s route, condition keys, endpoint policy, principal, actions, and resources. |
AWS recommends identifying allowed principals and granting specific actions rather than relying on wildcard principals and broad action patterns. A restrictive policy can also lock out legitimate callers or affect console use. Preserve an authorized administrative recovery path and consider all required callers before applying a deny. See AWS’s S3 access-control guidance and the 403 troubleshooting guide.
Test the fix against both routes
- Capture the failed server request’s principal, action, resource, source IP, timestamp, and endpoint route; record the equivalent details for a successful office request.
- Use the error context, CloudTrail events, or available request logs to identify the denied operation and narrow down the responsible policy layer. CloudTrail event details and availability depend on the logging configuration; consult AWS CloudTrail documentation.
- Adjust only the policy statement or condition needed to allow the intended principal, action, resource, and request path.
- Retest the exact failed operation from the server role, then verify the required office operation still works. Test other required actions separately, such as listing, reading, or writing.
If the 403 remains, revisit the actual principal and route first, then check the other authorization layers. A change to one policy does not establish that all relevant controls permit the request.
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