Resolve AWS API Gateway 403 Forbidden Error from VPC: Efficient Solution

Updated at: 05/06/2025

Accessing AWS API Gateway resources from your VPC? Encountering frustrating 403 Forbidden errors? This article delivers a streamlined solution to overcome this common hurdle. We'll dissect the root cause of this issue and provide practical, efficient steps to grant your VPC the necessary permissions to access your API Gateway endpoints, restoring seamless communication and functionality. Learn how to quickly resolve this problem and get back to building.

Methods: Disable Private DNS on VPC Endpoint

Step-by-Step Instructions

  1. Locate the VPC Endpoint

    • Check for a VPC endpoint for the execute-api service within your VPC.
    • Navigate to the VPC console in the AWS Management Console and choose endpoints in the left navigation panel.
    • Filter the VPC endpoints using the VPC ID and service name to find the execute-api endpoint.
    Filter the VPC endpoints using the VPC ID and service name to find the execute-api endpoint. Filter the VPC endpoints using the VPC ID and service name to find the execute-api endpoint. Filter the VPC endpoints using the VPC ID and service name to find the execute-api endpoint.
    Locate the VPC Endpoint

  2. Disable Private DNS

    • Select the VPC endpoint and choose 'Actions' then 'Modify private DNS names'.
    • Clear the check mark next to 'Enable' for the private DNS name setting.
    • Choose 'Modify private DNS names' to save the changes.
    Choose 'Modify private DNS names' to save the changes. Choose 'Modify private DNS names' to save the changes. Choose 'Modify private DNS names' to save the changes.
    Disable Private DNS

Tips

  • After disabling private DNS, clients using the private DNS name will need to use the public DNS name to connect to the private API.
  • Access the API using the AWS CLI with the public DNS name, passing the API ID in the x-api-gw-api-id header or using the host header.
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Common Mistakes to Avoid

1. Incorrect VPC Configuration

Reason: The VPC endpoint or NAT gateway isn't properly configured to allow outbound traffic to the API Gateway endpoint.
Solution: Ensure the VPC endpoint or NAT gateway has the necessary routes and security group rules to access the API Gateway.

2. Missing or Incorrect IAM Permissions

Reason: The IAM role associated with the application in the VPC lacks the necessary permissions to invoke the API Gateway.
Solution: Attach an IAM role with the appropriate `execute-api` permissions to the application's execution environment.

3. API Gateway Resource Policies Restrictions

Reason: The API Gateway's resource policy restricts access from the VPC's CIDR range.
Solution: Update the API Gateway's resource policy to explicitly allow access from the VPC's CIDR block.