Regarding Attack from one VM to another VM

If each node in the open nebula is considered as a user
launched VM in the cloud, then several VMs of different users can co-exist on the same physical machine. It is possible for one VM of another user which could attack the user VM in a variety of ways including stealing of information.

Is it correct?
Please correct me.

OpenNebula users and nodes -hosts- are different concepts. OpenNebula hosts are the physical machines that will run the VMs. OpenNebula natively supports three open source hypervisors, the KVM, LXD and Firecracker. On the other and OpenNebula supports user accounts and groups.

Therefore, you could attack a VM from another VM, for example, if you are able to exploit any kind of hypervisor vulnerability. You could also perform a network attack if you can reach the target VM -with a NIC attached to a Virutal Network- from a potential attacker, and the success of the attack will depend on the hardening configuration of the VM system.