CVE-2026-13218: KubeVirt virt-handler network cache symlink vulnerability allows arbitrary host file overwrite

A flaw was found in KubeVirt’s virt-handler network cache handling. The writeToCachedFile function writes data to a launcher-rooted path using os.WriteFile and os.Chown without symlink protection. A user with access to the virt-launcher container can plant a symlink at the cache file path, causing virt-handler to follow it and overwrite an arbitrary host file with JSON content and change its ownership.