Which headers are considered invalid by AWS in ALB attribute routing.http.drop_invalid_header_fields.enabled?

Question

I couldn't find any official AWS documentation on which headers are considered invalid by the Application Load Balancer when the routing.http.drop_invalid_header_fields.enabled attribute is enabled. Which of my headers will be dropped? Which characters are allowed and which are not? Is there a standard which is followed here?
I found this guide from TrendMicro but would still like to see some official AWS documentation:
https://www.trendmicro.com/cloudoneconformity/knowledge-base/aws/ELBv2/drop-invalid-header-fields-enabled.html

Accepted Answer

Hope this helps -
https://docs.aws.amazon.com/elasticloadbalancing/latest/application/application-load-balancers.html

routing.http.drop_invalid_header_fields.enabled
    Indicates whether HTTP headers with header fields that are not valid are removed by the load balancer (true), or routed to targets (false). The default is false. **Elastic Load Balancing requires that message header names conform to the regular expression [-A-Za-z0-9]+**, which describes all registered internet message headers. Each name consists of alphanumeric characters or hyphens.

Which headers are considered invalid by AWS in ALB attribute routing.http.drop_invalid_header_fields.enabled?

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