I had that panic yesterday on my main firewall.
Sorry it was urgent to put the system back online so I couldn't get more info.
I only got the trace, maybe it can help someone.
ddb{1}> trace
db_enter() at db_enter+0x14
panic(ffffffff8266de87) at panic+0xd5
__assert(ffffffff826ae92b,ffffffff8268e80b,8ba,ffffffff826a0cd1) at
__assert+0x29
pf_free_state(fffffd8148e4b1c0) at pf_free_state+0x28f
pf_purge_expired_states(22b4,40) at pf_purge_expired_states+0x2f8
pf_purge_states(0) at pf_purge_states+0x20
taskq_thread(ffffffff82a9e6a0) at taskq_thread+0x129
end trace frame: 0x0, count: -7
G
