Critical LXD Project Restriction Bypasses Enable Privilege and Quota Evasion

Canonical LXD disclosed and patched multiple flaws that let authenticated users bypass project-level restrictions during cross-project moves, copies, clustered migrations, and restore operations. The most severe issues, tracked as CVE-2026-63300 and CVE-2026-62420, carry CVSS 9.9 ratings and allow attackers with instance-creation rights in a restricted project to introduce disallowed instance configurations by first creating them in an unrestricted project or by abusing clustered migration flows that were treated as internal notifications. The bypasses could defeat controls such as restricted.containers.lowlevel, restricted.devices.*, and restricted.networks.access, potentially enabling host command execution or other high-impact policy violations.

A related flaw, CVE-2026-63299, lets authenticated users evade project disk and volume limits during cross-project storage volume moves and snapshot restores, with a CVSS 8.5 score. Canonical addressed the issues in LXD pull requests #18605 and #18651, adding validation of target-project restrictions for instance moves and copies, enforcing snapshot restrictions during backup restore, and hardening checks in the stable 5.21 branch. Organizations using LXD, especially clustered deployments and restricted multi-tenant projects, should upgrade to the latest patched release and review project restriction and migration controls.