Critical · CVSS 9.9CVE-2026-66897

Instance template path traversal allows arbitrary host file write as rootCVE-2026-66897

Answer in brief

CVE-2026-66897 records a Critical severity (CVSS 9.9) vulnerability in Instance template path traversal allows arbitrary host file write as root. The current sources do not mark it as known exploited. The current feed maps Canonical/LXD (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 24, 2026Updated Sep 11, 2026Source checked Oct 8, 2026First seen by HOL Aug 24, 2026Material review Sep 11, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.9
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Canonical/LXD (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:canonical:lxd::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Canonical/LXDgeneric	>=4.0.0 <4.0.13 \|\| >=5.0.0 <5.0.9 \|\| >=5.21.0 <5.21.7 \|\| >=6.0 <6.10	4.0.13, 5.0.9, 5.21.7, 6.10

Recommended response

Check inventory. Check lockfiles and deployed manifests for Canonical/LXD.
Review the reported fix. Source-reported solution: Upgrade to LXD versions 4.0.13, 5.0.9, 5.21.7, 6.10 or later.

Evidence timeline and material changes

Published upstream
Aug 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 24, 2026

Sources and claim methodology

GitHub security advisorygithub.com

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.