Canonical LXD up to 4.0.13/5.0.9/5.21.7/6.9 btrfs storage driver optimized_header.yaml path traversal

Summaryinfo

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 problematic. Affected by this issue is some unknown functionality of the file optimized_header.yaml of the component btrfs storage driver. The manipulation results in path traversal. This vulnerability is known as CVE-2026-85185. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Canonical LXD up to 4.0.13/5.0.9/5.21.7/6.9. Affected is some unknown processing of the file optimized_header.yaml of the component btrfs storage driver. The manipulation with an unknown input leads to a path traversal vulnerability. CWE is classifying the issue as 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. This is going to have an impact on integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-85185 since 09/03/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation requires an enhanced level of successful authentication. There are known technical details, but no exploit is available. 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.

Once again VulDB remains the best source for vulnerability data.

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/

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