Vulnerability · Published Aug 24, 2026 · Assigned by canonical
CVE-2026-66897Instance template path traversal allows arbitrary host file write as root
Critical 9.9
In plain English
A critical-severity path traversal in LXD from Canonical. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 54% of all known vulnerabilities).
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | lxd | no fix listed | DEBIAN-CVE-2026-66897 |
| Debian:13 | lxd | no fix listed | DEBIAN-CVE-2026-66897 |
Affected products (as reported)
Weakness: CWE-22, CWE-23 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
References
- https://github.com/canonical/lxd/security/advisories/GHSA-q39m-8fx9-42fv vdb-entry, vendor-advisory