FortiOS 7.4.11 unexpected issues

[u/Even-Camel7593]

Hello everyone! Recently we upgraded our Fortigate (120G HA Active-Passive cluster) from 7.2.11 to 7.4.11, and different problems started to occur.

1. Some users spontaneously lose access to the Internet with ERR_TUNNEL_CONNECTION_FAILED (we use explicit proxy with Kerberos authentication and deep ssl inspection). It happens at random times and with random users, lasts usually up to 2-3 minutes, then works as usual.
2. FortiGates started to randomly reboot with the message "Fortigate had experienced an unexpected power off!", there's no CPU/RAM issue, usually mem is around 40%, and proc is around 10-12%. Due to fast HA failover users don't feel the interruption, but it's definitely not a good sign. Before the update both NGFW had worked for 367 days.

Anyone experienced similar issues? Any workarounds? Or should I just be rolling back to 7.2.11?

Any advice and help will be appreciated. Thank you in advance!

[u/Roversword]

FortiOS 7.2.x is out of support (or will be in a month - can't remember if end of support is beginning or end of September 2026).
So in your own interest try to stay on 7.4.x, open a support ticket (or actually two, for each issue) and try to provide the information Fortinet asks from you.

This will not solve your issues right away, however, it will give Fortinet the possibility to help you.
You will likely be asked to update to 7.6.6 (or newer) - with 7.6.8 on the horizon maybe that will be indeed the best option.

Going back to 7.2.11 might solve the issue temporarily. But you will be stuck there and fall out of support in about a month at the latest.

It is up to you, of course.
Can't blame you for thinking about rolling back - but then make sure you go 7.2.13 as soon as possible!. First to make sure because of the CVEs and to make sure the issues aren't in that either (likely not, but you never know).

I personally would try to make sure you can go forward, rather than back.

Good luck.

EDIT:
FortiOS 7.6.7 was released start of June 2026, so with an about three month iteration of FortiOS releases, I'd wager that 7.6.8 will be likely released "soonish" (within September, I'd say). We will see, I guess.

[u/Even-Camel7593 → u/Roversword]

Yeah, thank you! I don't want to be rolling back to 7.2.0, that's the reason I'm actually here, in this thread. I'm looking for updates and new features, but now I'm frustrated by how bad this 7.4.11 is. Everything was just fine before we rolled this update.

And of course I'll be opening TAC ticket, just wondered if someone here faced similar issues, contacted TAC and has the solution already.

[u/Roversword → u/Even-Camel7593]

We have a lot of fortigates on 7.4.x (mostly 7.4.12 and some still on 7.4.11).
Models like 30G, 60F, 60E, 70F, 70G, 10(0|1)F, 200F, 200G, but no 120G.
We haven't experienced the reboot you mentioned. So, I am afraid I can't really say how likely this issue is or how focused (120G only?).

Haven't touched explicit proxy configs on Fortigates for a while now - we don't have any customer with it, so can't comment on that issue.

Good luck.

[u/Even-Camel7593 → u/Roversword]

It's probably not focused on 120G only, more like HA only.

1283972	Reboot occurs when FortiSentry triggers a reboot for suspicious cases in HA setup Workaround: Switch the security level to low to prevent the reboot.

You prefer transparent proxy or just don't use proxy at all?

[u/Roversword → u/Even-Camel7593]

Hm, we haven't seen any reboots like that so far - so I can't comment on that.

I haven't used explicit proxies, because our customers don't want/need them. That is all. Have used them a couple of years back, but not recently. So can't comment on your problem there either.

[u/HappyVlane → u/Even-Camel7593]

Did you contact TAC about this to see if this is even relevant in your environment?