# CVE-2026-66898: Path traversal via unvalidated instance name in backup tarball restore enables root file write / RCE

> Attackers can achieve root file write and remote code execution by crafting malicious backup archives with path traversal sequences in LXD.

- **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:** Yes
- **Published:** 12 Aug 2026
- **Updated:** 13 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-66898, GHSA-m857-c7gc-c984, UBUNTU-CVE-2026-66898

## What is CVE-2026-66898?

CVE-2026-66898 is a critical path traversal vulnerability in Canonical LXD, published on 12 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 allows an attacker to manipulate file system paths during backup import and restore operations. When importing or restoring a backup archive, LXD fails to validate instance and storage volume names contained within the archive metadata. An attacker can exploit this flaw by supplying a crafted backup archive with malicious instance or volume names containing path traversal sequences, potentially allowing file access or overwriting outside the designated restore directory.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-66898?

It affects 1 product.


Products: Canonical Lxd.

## How do I fix CVE-2026-66898?

Apply the vendor's patch.

## Is CVE-2026-66898 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66898 exists.

## Other vulnerabilities in Canonical LXD

- [CVE-2026-66897](https://insights.sbomify.com/CVE-2026-66897/): Instance template path traversal allows arbitrary host file write as root (critical 9.9)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66898 and fix it if it is affected.

What it is: CVE-2026-66898 is a critical path traversal vulnerability in Canonical LXD, published on 12 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66898 exists.

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-2026-66898/ (Markdown: https://insights.sbomify.com/CVE-2026-66898/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66898
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66898
- OSV: https://osv.dev/vulnerability/CVE-2026-66898

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66898/
Summaries are generated and may contain mistakes; the official description above is the record.