by Kastro
Paper/Archive/CVE-2026-66897

CVE-2026-66897

Canonical LXD — Instance template path traversal allows arbitrary host file write as root

EPSS 0.7%CVSS 9.9
critical.is priorityof 100
41
CVSS 9.9 (CNA)9.9 / 10 × 3029.7Not in CISA KEV+300.0EPSS percentile 53.8.538 × 2010.8No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
LXD4.0.0 – < 4.0.134.0.13CNA
LXD5.0.0 – < 5.0.95.0.9CNA
LXD5.21.0 – < 5.21.75.21.7CNA
LXD6.0 – < 6.106.10CNA

Scores by source

canonical (CNA)9.9CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: total

References

advisorygithub.com/canonical/lxd/security/advisories/GHSA-q39m-8fx9-42fv