High-severity host-root file overwrite via widely used Canonical LXD container platform; impacts many server/cloud deployments and warrants broad alerting.
CVE-2026-85526
Path traversal in LXD btrfs driver allows host file deletion/overwrite as root.
Is CVE-2026-85526 being exploited?
Not confirmed. CVE-2026-85526 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked.
How severe is CVE-2026-85526?
CVE-2026-85526 is rated Critical with a CVSS score of 9.9. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-85526?
Yes. A fix has been recorded for CVE-2026-85526. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-85526 affect?
CVE-2026-85526 affects Canonical LXD (btrfs storage driver), Linux hosts running LXD with btrfs optimized backups. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-85526?
Apply vendor LXD update immediately; restrict/revoke instance-creation privileges.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated user with instance-creation rights can delete or replace arbitrary host files as root via crafted btrfs backup import, enabling host takeover and data loss.
Immediate action required
- affected>= 4.0.0 and < 4.0.14
- affected>= 5.0.0 and < 5.0.10
- affected>= 5.21.0 and < 5.21.8
- affected>= 6.0 and < 6.10
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.