ModSecurity: Request body (Content-Length) is larger than the configured limit

Symptoms

Uploading content through a PHP script triggers a ModSecurity Error:

Request body (Content-Length) is larger than the configured limit

Description 

The data passed as an upload is normally part of a POST request, which sends data to the server. The error indicates that the site accepting the upload has placed the data in the body of a request that is not a POST request, which triggers an error from ModSecurity as it goes over the configured threshold.

For best results, the site itself should be reviewed by a developer to ensure that uploads are made in POST requests. The instructions below can be used as a temporary workaround.

Workaround

You can change the SecRequestBodyLimit setting within the ModSecurity configuration to raise the limit and allow the upload until the site can be reviewed by a developer:

1. Access the server as root via an SSH connection, or open the Terminal emulator within WHM.
2. Using a command-line text editor, open the following file for editing:
   

   /etc/apache2/conf.d/modsec/modsec2.user.conf

3. Add the following entry to the file. This is for a 10MB upload limit, but you can adjust the number value for the size that you require. There is a hard upper limit of 1GB:
   

   SecRequestBodyLimit 10485760

4. Save the file and exit the text editor
5. Use the built-in cPanel script to restart Apache and apply the changes:

   [root@server ~]# /scripts/restartsrv_httpd

Additional Resources

How to log into server using SSH?

Using Terminal To Access the Command Line

How to edit a file on command-line