VMware ESXi
TMA-ESXI9-5.7
Host should reject MAC address changes on standard virtual switches and port groups
Description
Enforcing MAC address stability on standard virtual switches and port groups prevents MAC impersonation by disallowing changes to the MAC address by virtual machines. This mitigates the risk of malicious activities initiated by impersonating authorized network adapters. The audit runs esxcli network vswitch standard (portgroup) policy security get for every standard vSwitch and port group and requires "Allow MAC Address Change: false". Runs in the ESXi Shell (busybox sh) as root.
How it is checked
Audit method: Shell command
command -v esxcli >/dev/null 2>&1 || exit 1
vs=$(esxcli network vswitch standard list 2>/dev/null | sed -n 's/^ *Name: *//p') || exit 1
pgs=$(esxcli --formatter=csv network vswitch standard portgroup list 2>/dev/null | awk -F, 'NR==1 {for (i = 1; i <= NF; i++) if ($i == "Name") c = i; next} c {print $c}') || exit 1
out=$(for v in $vs; do
x=$(esxcli network vswitch standard policy security get -v "$v" 2>/dev/null | sed -n 's/^ *Allow MAC Address Change: *//p' | head -n 1)
[ "$x" = false ] || echo "vSwitch $v: Allow MAC Address Change=${x:-unknown}"
done
printf '%s\n' "$pgs" | while IFS= read -r p; do [ -n "$p" ] || continue
x=$(esxcli network vswitch standard portgroup policy security get -p "$p" 2>/dev/null | sed -n 's/^ *Allow MAC Address Change: *//p' | head -n 1)
[ "$x" = false ] || echo "portgroup $p: Allow MAC Address Change=${x:-unknown}"
done)
[ -z "$out" ] && echo compliant || printf '%s\n' "$out"- Expected output
compliant
How it is fixed
Fix method: Guidance or infrastructure patch
To set the policy to reject, perform the following: 1. From the vSphere Web Client, select the host. 2. Click Configure then expand Networking. 3. Select Virtual switches then click Edit. 4. Click on Security. 5. Set MAC address changes to Reject in the dropdown. 6. Click on OK. Alternately, perform the following using the ESXi shell: # esxcli network vswitch standard policy security set -v vSwitch2 -m false
Properties
- Operating systems
- Any
- Tags
- vmwareesxinetwork
- Reference
- CIS VMware ESXi 9.0 Benchmark v1.0.0 - 5.7 Host should reject MAC address changes on standard virtual switches and port groups
Check this host
Run this on a machine you are allowed to audit. The scan is read-only.
tmaegis scan --target vmware