Paramiko version 2.4.1, 2.3.2, 2.2.3, 2.1.5, 2.0.8, 1.18.5, 1.17.6 contains a Incorrect Access Control vulnerability in SSH server that can result in RCE. This attack appear to be exploitable via network connectivity.
https://access.redhat.com/errata/RHBA-2018:3497
https://access.redhat.com/errata/RHSA-2018:3347
https://access.redhat.com/errata/RHSA-2018:3406
https://access.redhat.com/errata/RHSA-2018:3505
https://github.com/paramiko/paramiko/issues/1283
https://lists.debian.org/debian-lts-announce/2018/10/msg00018.html
https://lists.debian.org/debian-lts-announce/2021/12/msg00025.html
https://usn.ubuntu.com/3796-1/