FortiGate issue – some websites are suddenly no longer displayed

UPDATE 16.30 CEST: Cloudflare has resolved the issue. All workarounds can now be disabled, as they are no longer needed. The root cause has not yet been published. ERR_TIMED_OUT and ERR_EMPTY_RESPONSE being observed by Cloudflare Customers

127.10.2026, 14:45 CET: We are facing a spike in support requests regarding an issue that some websites are suddenly no longer displayed. We are investigating the issue in cooperation with Fortinet.

The issue might be related with an ongoing Cloudflare incident – but investigations are still in progress.

In the interim, we recommend applying one of the following temporary workarounds to mitigate the issue:

• Change the affected firewall policy to proxy-based mode.
• Temporarily disable UTM inspection on the affected policy.
• Change the tcp-mss for sender and receiver to 1300 bytes in the affected policies (as described here: https://community.fortinet.com/fortigate-3/troubleshooting-tip-web-pages-not-loading-or-taking-too-long-to-load-when-a-web-filter-is-applied-168097) or on the WAN interface (https://docs.fortinet.com/document/fortigate/7.6.8/cli-reference/317104469/config-system-interface#config-system-interface-2:~:text=Asynchronous%20transfer%20mode.-,tcp%2Dmss,-TCP%20maximum%20segment)
• Disable Kyber-Support in your Webbrowser (as described here: https://community.fortinet.com/fortigate-3/troubleshooting-tip-web-pages-not-loading-or-taking-too-long-to-load-when-a-web-filter-is-applied-168097)

We will provide further updates as soon as more information becomes available from the investigating team.