Stuck in Needbuf state, trying to understand (6.7)

Hello,

I have a script that mostly untar stuff on a vnd device.
And i have the same problem with syspatch

The program state gets into needbuf forever, ( the top state ).

I'm trying to figure out what is happening,
I have a feeling it may be an entropy exhaustion
but it's just a guess.

vmstat -m goes near 100% usage quickly
and swap/memory is like empty according to top.

Is it possible to get out of `vmstat -m` logged memory,
could it be a limit in login.conf that I reach without knowing ?

Once the problem is present, I cannot do anything but reboot
which does not help to understand what is going on.

Please hAlp.