500 OOPS: priv_sock_get_cmd

i am getting this error when i try to download file using vsftpd_v2.

some vsftpd versions are made faulty. So you should monitor it’s behaviour.

Some versions are faulty. So if you cant transfer a file then it could be intentional.
Try for other versions ans see if it is working.
If this fault is not observed in other versions then this was made intentional

can two or more versions be faulty? because when i tried with vsftpd_v2 and vsftpd_v3 their was this same error but it worked with vsftpd_v4.

Yes multiple version can show fault but not all of them.

What i mean is out of 7, 2 or w3 may have high cpu usage but not all of them (this is just an example)

And one more thing, If the version is showing fault in upload doesnt mean that it will show fault in download. So please check for both the directions