stay away from 5.2.8 if you are using IPV6
We have seen multiple crashes (kernel panics) during linux system upgrades (yum update, apt-get update) on ipv6 enabled servers.
Could be related to apply ctrl / ips / web filtering , but so far Fortinet was not really helpful in explaining why the crashes occurred. Fortinet answer (referring to a fixed bug in 5.4.1 that should be related):
>> The kernel panic is not related to yum specifically..
>> It is related to ipv6 traffic and from the notes is caused by kernel NULL pointer dereference for ipv6 traffic.
>> Now, it was remarked during the investigation that (at least in that case), the crash was caused when ftp
>> session helper was used by the traffic (which was tftp traffic). As soon as the tftp session helper was
>> removed the crash was not observed anymore.
But we didn't do any tftp at the time of the crashes, so in my opinion the problem is worse