LXD: Cross-guest storage volume hijacking (CVE-2026-12411)

LXD is susceptible to cross-guest volume hijacking due to missing ownership checks in the instance device-update path. When security.devlxd.management.volumes is enabled, the API fails to validate if an identity has ownership of a custom storage volume during a PATCH request to update instance devices. This enables a malicious guest to attach volumes belonging to other guests, resulting in full read/write access to the victim’s data. Volume names can be discovered via error probing.

Attack Chain

1. Attacker obtains a valid DevLXD identity with can_edit permissions for their own instance.
2. Attacker probes for volume names by attempting to attach them via PATCH requests to the DevLXD instance endpoint.
3. LXD processes the PATCH request for a disk device.
4. The devLXDInstancePatchHandler validates the device configuration shape (type, pool, source) but skips volume ownership/RBAC checks.
5. LXD attaches the victim's volume to the attacker's instance.
6. Attacker reads or overwrites data within the mounted volume at the specified mount point.

Impact

Exploitation allows for unauthorized access, modification, and potential data exfiltration of storage volumes belonging to other tenants within the same LXD project. The impact is limited to environments where security.devlxd.management.volumes is explicitly enabled.

Recommendation

• Upgrade LXD to the version containing the fix for CVE-2026-12411 (>= 0.0.0-20260626085133-7cb96ac80a6d).
• In environments where patching is deferred, disable security.devlxd.management.volumes for all instances in shared projects.
• Audit existing LXD instance configurations to identify unauthorized or unexpected disk devices.