Bad Request error on SonicWall Captive Portal

Problem

Users attempting to access the Captive Portal (https://192.168.x.x/auth.cgi) are presented with the following message:

Bad Request The client issued a bad request.

This usually appears when trying to access the Captive Portal over HTTPS, and the session is not initialized correctly or the browser makes an invalid request.

This error commonly occurs due to one or more of the following reasons:

• Attempting to access the Captive Portal over HTTPS without proper redirection or SSL certificate configuration.

• An expired or corrupted session cookie.

• Browser cache issues or stale session data.

• The Captive Portal web server on the SonicWall device may not be properly handling the request format.

Step 1: Access the Captive Portal over HTTP

Try using the HTTP version of the URL instead of HTTPS.
Example:
http://192.168.100.X/auth.cgi
This is because the default Captive Portal on SonicWall does not always handle HTTPS requests correctly without a valid certificate.

Step 2: Clear Browser Cache and Cookies

1. Clear your browser’s cache and cookies.

2. Close all browser windows.

3. Reopen and try accessing the portal again.

Step 3: Try a Different Browser or Incognito Mode

Sometimes, session data or browser extensions interfere with the portal loading correctly.

• Open the Captive Portal URL in Incognito/Private mode.

• Or, use a different browser entirely.

Step 4: Review SSL Certificate (If HTTPS is Required)

If HTTPS access is necessary:

• Ensure a valid SSL certificate is installed on the SonicWall device.

• Make sure the firewall is configured to handle SSL traffic for Captive Portal properly under:

  • Device |Users |Settings| Authentication method for login

  • And under Certificates |Common Name (CN) must match the IP or hostname being used.