CVE-2026-85185: Path traversal in LXD btrfs storage driver allows arbitrary file deletion and write on host as root
Path traversal in the btrfs storage driver in Canonical LXD versions 4.0.2 and later (fixed in 4.0.14, 5.0.10, 5.21.8 and 6.10) on Linux allows an authenticated client with permission to create instances in a project to delete arbitrary files on the host as root. On hosts whose root filesystem is btrfs, the client can also place attacker-controlled content at arbitrary host paths, leading to full host compromise. The client does this with a crafted subvolume path containing ../ sequences, sent in either of two ways: in the optimizedheader.yaml of an optimized btrfs backup, or in the btrfs migration header sent by a malicious migration source.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Canonical LXDto a version that resolves this vulnerability.Fixed in 4.0.14 - Upgrade
Upgrade
Canonical LXDto a version that resolves this vulnerability.Fixed in 5.0.10 - Upgrade
Upgrade
Canonical LXDto a version that resolves this vulnerability.Fixed in 5.21.8 - Upgrade
Upgrade
Canonical LXDto a version that resolves this vulnerability.Fixed in 6.10
Event History
Frequently Asked Questions
Who can exploit this vulnerability?
An authenticated LXD client must have permission to create instances in a project. Exploitation can be performed through a crafted optimized btrfs backup or by acting as a malicious migration source that supplies a crafted btrfs migration header.
Are all affected hosts exposed to full host compromise?
No. On affected Linux hosts, the flaw allows arbitrary file deletion on the host as root. Arbitrary placement of attacker-controlled content at host paths, and therefore full host compromise, is specifically described for hosts whose root filesystem is btrfs.
Which LXD releases contain fixes?
Fixes are available in LXD 4.0.14, 5.0.10, 5.21.8, and 6.10. The affected versions are described as 4.0.2 and later.