CVE-2026-85185 Path traversal in LXD btrfs storage driver allows arbitrary file deletion and write on host as root
Authenticated users can delete or write arbitrary host files as root via path traversal in the btrfs storage driver, leading to host compromise.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-85185?
CVE-2026-85185 is a critical path traversal vulnerability in Canonical LXD, published on 28 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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 optimized_header.yaml of an optimized btrfs backup, or in the btrfs migration header sent by a malicious migration source.
Weakness: CWE-22
Which versions are affected by CVE-2026-85185?
How do I fix CVE-2026-85185?
Upgrade to a fixed version.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-85185 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-85185 exists.
Sources
Also known as DEBIAN-CVE-2026-85185, GHSA-27q7-qwhm-c34p, UBUNTU-CVE-2026-85185.