It looks like Unraid 6.12.8 itself is not impacted. I checked the version on mine and version 5.4.1 was returned which is not one of the version listed as impacted (5.6.0 and up)
https://nvd.nist.gov/vuln/detail/CVE-2024-3094
https://access.redhat.com/security/cve/cve-2024-3094
You should check any containers you have running.
xz --version will return the current version