CVE-2026-66897

Instance template path traversal allows arbitrary host file write as root

Published Aug 24, 2026 CVSS 3.1 · 9.9 Critical EPSS < 1% KEV · Not listed
Description
A path traversal vulnerability in LXD's instance template processing allows an attacker with container edit permissions, or any user launching a crafted image, to overwrite arbitrary files on the host system as root. When processing target template paths specified in metadata.yaml, LXD validates the path against a confined os.Root directory handle but subsequently opens and creates the file using os.Create with an unconfined string path. This discrepancy between path resolution checks and file creation allows an attacker to escape directory confinement, overwrite root-owned host files, and achieve host root code execution.

Remediation

Vendor Solution

Upgrade to LXD versions 4.0.13, 5.0.9, 5.21.7, 6.10 or later.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
CPEs cpe:2.3:a:canonical:lxd:*:*:*:*:*:*:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Canonical
Canonical lxd
Vendors & Products Canonical
Canonical lxd
Type Values Removed Values Added
Description A path traversal vulnerability in LXD's instance template processing allows an attacker with container edit permissions, or any user launching a crafted image, to overwrite arbitrary files on the host system as root. When processing target template paths specified in metadata.yaml, LXD validates the path against a confined os.Root directory handle but subsequently opens and creates the file using os.Create with an unconfined string path. This discrepancy between path resolution checks and file creation allows an attacker to escape directory confinement, overwrite root-owned host files, and achieve host root code execution.
Title Instance template path traversal allows arbitrary host file write as root
Weaknesses CWE-22
CWE-23
References
Metrics cvssV3_1

{'score': 9.9, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
canonical
Published
Updated
Aug 25, 2026, 3:55 AM
Reserved
Jul 28, 2026, 7:41 AM
Status
Analyzed
Published
Aug 24, 2026, 10:16 AM
Modified
Oct 24, 2026, 4:10 PM