# CVE-2026-66897: Instance template path traversal allows arbitrary host file write as root

> Attackers can overwrite host files as root via path traversal in LXD instance templates, leading to host code execution.

- **Severity:** Critical 9.9 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-66897, GHSA-q39m-8fx9-42fv, UBUNTU-CVE-2026-66897

## What is CVE-2026-66897?

CVE-2026-66897 is a critical path traversal vulnerability in Canonical LXD, published on 24 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-23 (Relative Path Traversal), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-66897?

It affects 1 product.


Products: Canonical Lxd.

## How do I fix CVE-2026-66897?

No fix has been published for CVE-2026-66897 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-66897 being exploited?

There is no known exploitation of CVE-2026-66897 in the wild and no public exploit code.

## Other vulnerabilities in Canonical LXD

- [CVE-2026-62420](https://insights.sbomify.com/CVE-2026-62420/): Cross-project cluster migration bypasses project restrictions via cluster notification flag (critical 9.9)
- [CVE-2026-63293](https://insights.sbomify.com/CVE-2026-63293/): Arbitrary File Read/Write: metadata.yaml symlink in image allows host filesystem access as root (critical 9.9)
- [CVE-2026-63294](https://insights.sbomify.com/CVE-2026-63294/): Root RCE via image backup.yaml symlink (critical 9.9)
- [CVE-2026-63296](https://insights.sbomify.com/CVE-2026-63296/): Project restriction bypass via instance migration config override (critical 9.9)
- [CVE-2026-63297](https://insights.sbomify.com/CVE-2026-63297/): Cross-project instance copy bypasses target project restrictions via TOCTOU in config merge (critical 9.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66897 and fix it if it is affected.

What it is: CVE-2026-66897 is a critical path traversal vulnerability in Canonical LXD, published on 24 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-66897 in the wild and no public exploit code.

Affected product: Canonical LXD. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-66897/ (Markdown: https://insights.sbomify.com/CVE-2026-66897/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66897
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66897
- OSV: https://osv.dev/vulnerability/CVE-2026-66897

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66897/
Summaries are generated and may contain mistakes; the official description above is the record.