Path traversal via Btrfs optimized-backup subvolumes[].path enables root file/dir manipulation in LXD (CVE-2026-85526) | HOL Guard CVE

Critical · CVSS 9.9CVE-2026-85526

Path traversal via Btrfs optimized-backup subvolumes[].path enables root file/dir manipulation in LXD

Answer in brief

CVE-2026-85526 records a Critical severity (CVSS 9.9) vulnerability in Path traversal via Btrfs optimized-backup subvolumes[].path enables root file/dir manipulation in LXD. 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 Sep 28, 2026Updated Sep 28, 2026Source checked Sep 28, 2026First seen by HOL Sep 28, 2026Material review Sep 28, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.9
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
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.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Canonical/LXDgeneric	>=4.0.0 <4.0.14 \|\| >=5.0.0 <5.0.10 \|\| >=5.21.0 <5.21.8 \|\| >=6.0 <6.10	4.0.14, 5.0.10, 5.21.8, 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 4.0.14, 5.0.10, 5.21.8, 6.10 or later.

Evidence timeline and material changes

Published upstream
Sep 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 28, 2026

Sources and claim methodology

Upstream source description

Path traversal in the Btrfs storage driver (unpackVolume) in Canonical LXD on Linux allows an authenticated user with instance creation privileges to delete or replace arbitrary files and directories on the host filesystem as root via a crafted subvolumes[].path entry in backup/optimized_header.yaml during a btrfs optimized backup import.

Quoted source text, attributed separately from HOL analysis.