# CVE-2026-9639: Authenticated Denial of Service via Malicious Backup Tarball in LXD

> An authenticated user can cause a denial of service in LXD by uploading a malicious backup tarball that triggers a null pointer dereference.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 26 Jun 2026
- **Updated:** 26 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-9639, GHSA-j93m-3j9p-m5m8

## What is CVE-2026-9639?

CVE-2026-9639 is a medium-severity vulnerability in Canonical LXD, published on 26 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Nil-pointer dereference in CreateCustomVolumeFromBackup in LXD up to version 6.8 and 5.21 on Linux allows an authenticated user with can_create_storage_volumes permissions to cause a denial of service via a specially crafted custom-volume backup tarball that omits the expires_at snapshot field.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-9639?

It affects 1 product.


Products: Canonical Lxd.

## How do I fix CVE-2026-9639?

Apply the vendor's patch.

## Is CVE-2026-9639 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-9639 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-2026-9639 and fix it if it is affected.

What it is: CVE-2026-9639 is a medium-severity vulnerability in Canonical LXD, published on 26 Jun 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-2026-9639 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-2026-9639/ (Markdown: https://insights.sbomify.com/CVE-2026-9639/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-9639
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-9639
- OSV: https://osv.dev/vulnerability/CVE-2026-9639

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-9639/
Summaries are generated and may contain mistakes; the official description above is the record.