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Project Restriction Bypass in LXD instancePostMigration
CVE-2026-63300 is an improper validation vulnerability in Canonical LXD affecting the instancePostMigration function in lxd/instance_post.go. During cross-project instance migration, LXD does not correctly validate the instance configuration and associated snapshot state against the destination project's enforced restrictions. As a result, an authenticated attacker who has permission to create instances in a restricted project can first create an instance in a less restricted or unrestricted project using configuration that would normally be disallowed by the target project, and then move that instance into the restricted project. This bypass can defeat project-level controls including low-level container restrictions, device restrictions, and network access restrictions. The flaw stems from missing enforcement of target-project policy during the migration path rather than during initial instance creation.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation allows bypass of project isolation and policy enforcement in LXD. An attacker can place a disallowed or higher-privilege instance into a restricted project despite that project's configured security controls. Depending on the forbidden configuration introduced through the bypassed migration path, impact can include unauthorized access to restricted devices or networks, execution of operations that should be blocked by project policy, and potentially host-level command execution. The vulnerability therefore affects confidentiality, integrity, and availability and can undermine multi-tenant or delegated-administration security boundaries implemented through LXD project restrictions.
If you can’t patch tonight, do this now.
If immediate patching is not possible, restrict or temporarily disable cross-project instance migration and closely limit which users or roles are granted instance-creation capabilities in restricted projects. Reduce exposure by avoiding mixed-trust use of unrestricted and restricted projects under the same administrative domain, and review project policies and operational workflows to ensure that instance relocation cannot be used as a policy-bypass mechanism. Additional monitoring of cross-project move activity can help detect attempted exploitation until patched versions are deployed.
Patch, then assume compromise.
Upgrade LXD to a version that enforces destination-project restriction checks during cross-project instance migration. The fix adds validation so that an instance and its snapshots are checked against the target project's limits and restrictions before the move is accepted. Related hardening also extends restriction enforcement to cross-project copy paths and snapshot-related restore scenarios. After upgrading, verify that project restriction policies are consistently enforced for instance moves, copies, and restore workflows.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.