Cloud
CVE-2026-85526
Path traversal in LXD btrfs driver allows host file deletion/overwrite as root.
Major vulnerability. High-severity host-root file overwrite via widely used Canonical LXD container platform; impacts many server/cloud deployments and warrants broad alerting.
- CVSS
- 9.9Criticalscored by the publisher (CNA)
- Exploited in the wild
- Not knownpublic proof of concept per CISA SSVC; not in CISA KEV
- EPSS
- 0.53%chance of exploitation in the next 30 daystop 55% of scored CVEsFIRST score of 12 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 28 Sept 2026analysed here 28 Sept 2026
Summary
Impact
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.
Triage
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Canonical LXD | >= 4.0.0 and < 4.0.14>= 5.0.0 and < 5.0.10>= 5.21.0 and < 5.21.8>= 6.0 and < 6.10Vendor says fixed in: not stated |
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.
Products named in our analysis
- Canonical LXD (btrfs storage driver)
- Linux hosts running LXD with btrfs optimized backups
Fix and mitigation
Action required
Immediate action required
WAF and other mitigations
Can a WAF block it? No. The vulnerability involves path traversal in the LXD btrfs driver, which requires local access to the host running LXD. It is not triggered via HTTP requests, so a web application firewall cannot filter or block the attack.
Also consider: canonical path validation
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Not listed as of our last sync.
- Public exploit code
- None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
- CISA SSVC
- exploitation poc, automatable no, technical impact totalAssessed by CISA 28 Sept 2026 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Timeline
- 28 Sept 2026CISA SSVC assessment: exploitation poc
- 28 Sept 2026Published1 day later
- 28 Sept 2026Analysed by vulneraibility.comsame day later
- 29 Sept 2026CVE record last updated1 day later
Common questions
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. EPSS currently estimates a 0.53% probability of exploitation in the next 30 days.
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.
References
6 references in the CVE record, grouped by the tags the record gives them.
Advisories (1)
- github.com /canonical/lxd/security/advisories/GHSA-h85r-gjgx-g2rv
Patches (5)
- github.com /canonical/lxd-private/pull/87
- github.com /canonical/lxd-private/pull/105
- github.com /canonical/lxd-private/pull/104
- github.com /canonical/lxd-private/pull/103
- github.com /canonical/lxd-private/pull/84
Also tracked as GHSA-h85r-gjgx-g2rv (OSV).
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- OSV: advisory aliases and downstream package versions
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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