Path traversal in the Btrfs storage driver (unpackVolume) in Canonical LXD on Linux allows an authenticated user with instance creation privileges… (CVE-2026-85526)
Description
A path traversal vulnerability exists in the Btrfs storage driver (unpackVolume) of Canonical LXD on Linux. This flaw allows an authenticated user with instance creation privileges to delete or replace arbitrary files and directories on the host filesystem as root by crafting a malicious subvolumes[].path entry in backup/optimized_header.yaml during a btrfs optimized backup import.
CVSS v3.1
Score 9.9critical
Affected software
pkg:deb/ubuntu/lxd?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/lxd?arch=source&distro=esm-infra/bionicpkg:deb/ubuntu/lxd?arch=source&distro=focalpkg:deb/ubuntu/incus?arch=source&distro=esm-apps/noblepkg:deb/ubuntu/incus?arch=source&distro=stonkingpkg:deb/ubuntu/incus?arch=source&distro=esm-apps/resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-85526 is a path traversal vulnerability in the Btrfs storage driver (unpackVolume) component of Canonical LXD on Linux. An authenticated user who has privileges to create instances can exploit this vulnerability by providing a specially crafted subvolumes[].path entry in the backup/optimized_header.yaml file during the import of a btrfs optimized backup. This allows the attacker to delete or replace arbitrary files and directories on the host filesystem with root privileges, leading to full system compromise. The vulnerability affects multiple specific versions of LXD as listed, and has a CVSS v3.1 base score of 9.9, indicating critical severity.
Potential Impact
Successful exploitation of this vulnerability results in an authenticated user with instance creation privileges gaining root-level control over the host filesystem by deleting or replacing arbitrary files and directories. This can lead to full system compromise, data loss, or persistent unauthorized access.
Mitigation Recommendations
No explicit patch or remediation information is provided in the input data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is applied, restrict instance creation privileges to trusted users only and avoid importing untrusted btrfs optimized backups.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-85526
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:Pro:24.04:LTS","Ubuntu:26.10","Ubuntu:Pro:26.04:LTS"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ad3f5552cdf04f65665e938
Added to database: 10/17/2026, 22:23:17 UTC
Last enriched: 10/17/2026, 23:26:26 UTC
Last updated: 10/17/2026, 23:26:26 UTC
Views: 2
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