LXD (Incus) contains a vulnerability in its backup compression algorithm handling that allows argument injection. The software validates only the first token of the user-supplied compression algorithm against an allowlist but does not reject extra arguments. This flaw enables an attacker to inject additional command-line arguments, leading to arbitrary file writes on the host system and potentially arbitrary command execution. A proof-of-concept demonstrates uploading a malicious cron job file via this injection. The vulnerability is rated critical with a CVSS score of 9.9 and has been patched in version 0.0.0-20260630083100-c5184be310b1.