Why does cPFence require SSSE3?

cPFence requires SSSE3 CPU instructions for its high-performance security scanning engine. If the server’s CPU does not expose them, cPFence stops with this error:

Error: This CPU does not support SSSE3.

SSSE3 is a well-established instruction set supported by virtually all modern Intel and AMD server processors. It is also part of the x86-64-v2 architecture baseline, which is a minimum requirement for major enterprise Linux distributions, including Red Hat Enterprise Linux 9 and Rocky Linux 9.

If your VPS does not expose SSSE3, your virtualization provider may be using an outdated or overly restrictive virtual CPU configuration. The official QEMU documentation explicitly discourages legacy CPU models such as kvm64 because they expose limited CPU features and prevent optimal performance.

Check SSSE3 support

Run this on the server:

grep -qw ssse3 /proc/cpuinfo && echo "SSSE3 Supported" || echo "SSSE3 Not Supported"

Enable SSSE3 in Proxmox VE

If you use Proxmox VE, change the VM’s CPU type:

1. Open the Proxmox web interface and select your VM.
2. Go to Hardware → Processors → Edit.
3. Change CPU Type to host (recommended for standalone servers), or to x86-64-v2-AES if you need better compatibility for VM migration.
4. Select OK, then fully shut down and start the VM to apply the change. A reboot from inside the VM is not enough.

More details are in the official Proxmox CPU documentation.

Choosing a CPU type

The host CPU type exposes the physical processor’s features to the VM, but may limit live migration between servers with different CPUs. Both options require a compatible physical processor.

Other platforms and VPS providers

If you use another virtualization platform or a third-party VPS provider, ask your provider to expose SSSE3 CPU instructions to your VPS, preferably by enabling an x86-64-v2 or newer CPU model. Then run the check above again before installing cPFence.