FortiOS 8.0.2: HTTPS sites on non-standard ports fail with ERR_EMPTY_RESPONSE with deep inspection
Summary
After upgrading to FortiOS 7.2.14, 7.4.13, 7.6.8 or 8.0.2, websites on non-standard HTTPS ports fail when deep inspection is enabled. Fortinet lists this as a known issue (Bug ID 1353958, area Explicit Proxy). No workaround or fix is documented yet.
Symptoms
The client browser shows net::ERR_EMPTY_RESPONSE only for websites on non-standard HTTPS ports (for example 8443 or 8011) with deep inspection enabled. Websites on standard HTTPS ports work as expected.
Affected
- FortiOS 7.2.14
- FortiOS 7.4.13
- FortiOS 7.6.8
- FortiOS 8.0.2
- Only traffic with deep inspection enabled to non-standard HTTPS ports (Bug ID 1353958, Explicit Proxy)
Workaround
No workaround known.
Fix
Not fixed yet.
Recommendation
Before upgrading to one of the affected versions, check whether internal or external services on non-standard HTTPS ports (such as management portals on 8443) are reached through deep inspection, and test them in a pilot. If you already upgraded and are affected, follow the Fortinet release notes for updates and consider delaying further rollouts.
Sources
- FortiOS 8.0.2 Release Notes: Known issues Vendor · docs.fortinet.com
Compiled from the sources listed and translated with AI (Claude); status and dates come from the vendor. The vendor’s statements are authoritative. Updated 1 Nov 2026, 22:02.
Where the information comes from
We continuously read the vendors’ official sources, community reports and trade media and summarise them in our own words, with a link to the source:
- Microsoft: Windows release health (Windows 10/11, Server 2016 to 2025), Windows message center, known issues of Microsoft 365 Apps (Outlook, Excel, Word, PowerPoint), Edge, Intune, Autopilot, Windows 365 and Entra Connect, Microsoft KB articles with timelines, Exchange and Windows IT Pro blogs, optionally Microsoft 365 service health and message center
- other vendors: Veeam KB, Citrix (known issues), Ubuntu and Debian (regressions), Broadcom (VMware), Fortinet, Cisco, Mozilla, Let’s Encrypt
- community (title, short excerpt and link only, without the names of the authors): Microsoft Q&A, Microsoft Tech Community (discussions), Veeam R&D Forums, Eleven Forum
- targeted web research with AI (Claude), e.g. on the updates of the month – this also finds discussions on Reddit and in forums; such entries are labelled as community reports until the vendor confirms them
- early warning from trade media (title and link only): Born’s Tech and Windows World, BleepingComputer, AskWoody, Windows Latest, Windows Central, gHacks, The Windows Club, Deskmodder, Dr. Windows, WindowsArea, Frankys Web, heise online
Summary and translation with AI (Claude by Anthropic) – without any data of visitors.
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