Unexpected 403 errors sent by Cloudfront to some clients server requests

Hi,

Since the last week-end (Aug 1st), one our clients is receiving 403 when trying to POST to one of our CloudFront endpoints from some of their servers. The others are working fine. We are wondering what is going on.

The cloud front in question is associated with a WAF, the origin is API Gateway HTTP → Lambda.

We're not seeing the 403 in lambda cloudwatch logs, so we're expecting these to be produced by CloudFront, the WAF or API Gateway.

The following response is received by our client:
Received Unsuccessful status code : 403 response was : HttpResponseProxy{HTTP/1.1 403 Forbidden [Server: CloudFront, Date: Tue, 03 Aug 2021 12:35:09 GMT, Content-Type: text/html, Content-Length: 919, Connection: keep-alive, X-Cache: Error from cloudfront, Via: 1.1 7f5e0d3b9ea85d0d75063a66c0ebc841.cloudfront.net (CloudFront), X-Amz-Cf-Pop: HIO50-C1, X-Amz-Cf-Id: FRj76DTVztpUV4MJzAH2yL-mZOy4Ac9dm5RuAEWXhCOxAtiu9PVxmQ==] ResponseEntityProxy{[Content-Type: text/html,Content-Length: 919,Chunked: false]}}

What can we do to investigate further?

Edited by: bdo-discovery on Aug 4, 2021 11:19 PM