Troubleshooting Tip: How to resolve HTTP/2 'Header List Size in SETTINGS Frame Exceeded' error on FortiWeb

Description

This article describes how to resolve the HTTP/2 'Header List Size Exceeded' error on FortiWeb. This issue may occur when the request header size exceeds the allowed limit, resulting in the connection being blocked.

Scope

FortiWeb.

Solution

From the GUI, navigate to Web Protection -> Protocol -> HTTP, then adjust the Header List Size to meet the requirements of the environment.

Alternatively, HTTP protocol constraints can be configured from the CLI.

1. Use the following command to enter the HTTP protocol parameter restriction configuration:

config waf http-protocol-parameter-restriction

2. Edit the required HTTP protocol constraint:

edit <HTTP-Protocol-Constraint-Name>

3. Enable the header list size check:

set max-setting-header-list-size-check enable

4. Define the maximum header list size value:

set max-setting-header-list-size <input_value>

5. Save the configuration:

end

Related document:

HTTP/HTTPS protocol constraints