CVE-2026-85526 Path traversal via Btrfs optimized-backup subvolumes[].path enables root file/dir manipulation in LXD
Authenticated users can delete or replace arbitrary host files as root via path traversal in LXD Btrfs backup imports.
- 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-2026-85526?
CVE-2026-85526 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 (unpackVolume) in Canonical LXD on Linux allows an authenticated user with instance creation privileges to delete or replace arbitrary files and directories on the host filesystem as root via a crafted subvolumes[].path entry in backup/optimized_header.yaml during a btrfs optimized backup import.
Weakness: CWE-22
Which versions are affected by CVE-2026-85526?
How do I fix CVE-2026-85526?
Apply the vendor's patch.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-85526 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-85526 exists.
Sources
Also known as DEBIAN-CVE-2026-85526, GHSA-h85r-gjgx-g2rv, UBUNTU-CVE-2026-85526.