On systems where at least one OCI remote is configured (most common on Fedora systems), a malicious local user in an active local session could use a crafted architecture name to trick the flatpak-system-helper process into creating a root-owned directory tree with contents determined by the OCI remote, plus a root-owned lock file and icons directory, outside the intended root directory.

If this vulnerability is combined with other vulnerabilities also fixed in 1.18.1, the combination can lead to local root privilege escalation.