Architect Data Action calling AWS Lambda returns 403 Forbidden - IAM Policy Issue?

Architect & Flows
1

Could use a hand troubleshooting this persistent 403 Forbidden error when trying to invoke an AWS Lambda function from a CXone Architect Data Action. I’ve been coming from Five9, so the IAM model here feels a bit more restrictive than what I’m used to, and I want to make sure I’m not missing a basic configuration step.

Here is the flow:

  1. I have a Data Action in Architect configured to make a POST request to our Lambda URL.
  2. The Lambda function is simple; it just echoes back the input payload for testing.
  3. The request fails immediately with a 403 status code.

I’ve verified that the Lambda function itself is working by invoking it directly via the AWS CLI and it returns a 200 OK with the expected JSON. So the issue seems to be with how CXone is authenticating or authorizing the call.

“When invoking a Lambda function via a Lambda URL, you must configure the Lambda function’s CORS settings and ensure the IAM role used by the calling service has the lambda:InvokeFunctionUrl permission attached.”

I created an IAM role for the CXone integration and attached a policy that looks like this:

{
 "Version": "2012-10-17",
 "Statement": [
 {
 "Effect": "Allow",
 "Action": "lambda:InvokeFunctionUrl",
 "Resource": "arn:aws:lambda:us-east-1:123456789012:function:my-test-lambda"
 }
 ]
}

I’m assuming the Data Action uses a default service role or perhaps I need to configure a specific trust relationship? I haven’t found clear documentation on whether CXone Data Actions assume a role or just make an anonymous public call (which seems unlikely for security).

Is there a specific IAM policy document I should be attaching, or do I need to configure the Lambda URL auth type to ‘NONE’ for testing? Any pointers on the correct IAM setup for this scenario would be greatly appreciated.

2

The docs actually state that AWS Lambda URLs require specific authorization types, and the default is often AWS_IAM. This explains the 403 Forbidden error you are seeing. Your Genesys Cloud Data Action is likely sending a standard POST without the necessary AWS Signature Version 4 headers, which AWS rejects immediately.

Here is the fix:

  1. Change Authorization: In the AWS Lambda console, navigate to Configuration > Configuration > Lambda URL. Change the Authentication setting from AWS_IAM to NONE. This allows public invocation without signing requests.
  2. Update Architect: Ensure your Data Action in CXone Architect is set to POST and includes the correct Content-Type header (application/json).
  3. Verify Payload: Check that the request body matches the expected schema of your Lambda function.

If you cannot disable IAM auth for security reasons, you must use a Lambda Function URL with an API Gateway in front of it, or sign the request manually in Genesys Cloud using a pre-request script, which is significantly more complex.

3

The documentation actually says Lambda URLs default to AWS_IAM auth, which explains the 403. Genesys Cloud Data Actions do not sign requests with Signature Version 4.

  • Go to your Lambda configuration in AWS.
  • Set the authorization type to NONE.
  • Test the Data Action again.
4

Check your Lambda URL authorization settings. Disabling auth entirely as suggested above is a temporary fix but introduces significant security risks, especially if the endpoint processes PII or triggers outbound actions. Genesys Cloud Data Actions do not support AWS Signature Version 4 signing out of the box, so AWS_IAM will always fail. Instead of opening the endpoint to the world, implement a simple header-based verification in your Lambda code to validate the request source. This approach maintains security without requiring complex IAM role assumptions that Genesys Cloud cannot perform.

“The documentation actually says Lambda URLs default to AWS_IAM auth, which explains the 403. Genesys Cloud Data Actions do not sign requests with Signature Version 4.”

You are correct that SigV4 is the blocker, but setting authorization to NONE is dangerous. I use a custom header in the Genesys Cloud Data Action (e.g., X-GC-Secret: myStaticKey) and validate it in the Lambda handler. This is lightweight and effective. Below is a Python snippet for the Lambda function that rejects unauthorized requests immediately. Ensure you add this header in the Data Action configuration under “Headers”.

import json

def lambda_handler(event, context):
 # Extract headers from the event
 headers = event.get('headers', {})
 
 # Define your secret key
 SECRET_KEY = "myStaticKey"
 
 # Check for the custom header
 if headers.get('x-gc-secret') != SECRET_KEY:
 return {
 'statusCode': 403,
 'body': json.dumps({'error': 'Unauthorized request'})
 }
 
 # Process the valid request
 return {
 'statusCode': 200,
 'body': json.dumps({'message': 'Success', 'input': event.get('body')})
 }

This method avoids exposing your Lambda to public internet noise while bypassing the SigV4 limitation. Never rely on IP whitelisting alone as Genesys Cloud egress IPs are dynamic and numerous.

5 
if request.headers.get("X-GC-Source") != "trusted_id":
 return {"statusCode": 403, "body": "Unauthorized"}

You might want to look at header validation. Disabling auth exposes PII. My gRPC service rejects unsigned requests. 1. Add a static header in the Data Action. 2. Verify it in Lambda. This balances security with GC’s lack of SigV4 support.