Instance template path traversal allows arbitrary host file write as root

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-66897
StatePUBLISHED
Assignercanonical
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-24 10:16:39 UTC
Updated2026-09-11 15:28:53 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 9.9 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS: 0.006190000 probability, percentile 0.472030000 (date 2026-08-30)

Problem Types: CWE-22 | CWE-23 | CWE-22 CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') | CWE-23 CWE-23: Relative Path Traversal

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.9CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
3.1CNACVSS9.9CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Canonical Lxd All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Canonical LXD affected 4.0.0 4.0.13 semver Linux
CNA Canonical LXD affected 5.0.0 5.0.9 semver Linux
CNA Canonical LXD affected 5.21.0 5.21.7 semver Linux
CNA Canonical LXD affected 6.0 6.10 semver Linux

References

ReferenceSourceLinkTags
github.com/canonical/lxd/security/advisories/GHSA-q39m-8fx9-42fv [email protected] github.com Vendor Advisory, Exploit
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Solutions

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

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