Canonical LXD up to 4.0.13/5.0.9/5.21.7/6.9 Btrfs storage driver optimized_header.yaml unpackVolume subvolumes[] path traversal

Summaryinfo

A vulnerability labeled as very critical has been found in Canonical LXD up to 4.0.13/5.0.9/5.21.7/6.9. Impacted is the function unpackVolume of the file backup/optimized_header.yaml of the component Btrfs storage driver. Executing a manipulation of the argument subvolumes[] can lead to path traversal. The identification of this vulnerability is CVE-2026-85526. The attack may be launched remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Canonical LXD up to 4.0.13/5.0.9/5.21.7/6.9. It has been declared as very critical. This vulnerability affects the function unpackVolume of the file backup/optimized_header.yaml of the component Btrfs storage driver. The manipulation of the argument subvolumes[] with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-85526 since 09/04/2026. The exploitation appears to be easy. The attack can be initiated remotely. Additional levels of successful authentication are needed for exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/28/2026). The MITRE ATT&CK project declares the attack technique as T1006.

Upgrading to version 4.0.14, 5.0.10, 5.21.8 or 6.10 eliminates this vulnerability.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• Canonical

Name

• LXD

Version

• 4.0.0
• 4.0.1
• 4.0.2
• 4.0.3
• 4.0.4
• 4.0.5
• 4.0.6
• 4.0.7
• 4.0.8
• 4.0.9
• 4.0.10
• 4.0.11
• 4.0.12
• 4.0.13
• 5.0.0
• 5.0.1
• 5.0.2
• 5.0.3
• 5.0.4
• 5.0.5
• 5.0.6
• 5.0.7
• 5.0.8
• 5.0.9
• 5.21.0
• 5.21.1
• 5.21.2
• 5.21.3
• 5.21.4
• 5.21.5
• 5.21.6
• 5.21.7
• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6
• 6.7
• 6.8
• 6.9

License

• open-source

Website

• Product: https://github.com/canonical/lxd/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion