# CVE-2026-97206: DNS-over-QUIC (DoQ) path-migration can lead to use-after-free on multi-threaded deployments.


- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 21 Oct 2026
- **Updated:** 29 Oct 2026
- **Also known as:** AZL-109824, DEBIAN-CVE-2026-97206, ECHO-c92f-53fb-23d0, GHSA-jc7q-6h55-rr57, UBUNTU-CVE-2026-97206

## What is CVE-2026-97206?

CVE-2026-97206 is a high-severity vulnerability in NLnet Labs Unbound, published on 21 Oct 2026. 

### Official description

NLnet Labs Unbound, 1.22.0 up to and including version 1.26.1, contains a DNS-over-QUIC (DoQ) lifetime bug reachable by a remote DoQ client under multi-threaded operation. A client-triggered QUIC path migration can enter stream/connection cleanup while a mesh reply still retains a pointer to the DoQ stream. Cleanup frees the DoQ stream and when the pending mesh reply later completes it dereferences a stale pointer leading to a crash.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-97206?


## How do I fix CVE-2026-97206?

Upgrade to a fixed version.

## Is CVE-2026-97206 being exploited?

There is no known exploitation of CVE-2026-97206 in the wild and no public exploit code.

Public exploit code:

- https://github.com/suominen/CVE-2026-97206 (github_poc): https://github.com/suominen/CVE-2026-97206

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97206 and fix it if it is affected.

What it is: CVE-2026-97206 is a high-severity vulnerability in NLnet Labs Unbound, published on 21 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-97206 in the wild and no public exploit code.

Affected product: NLnet Labs Unbound. 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-2026-97206/ (Markdown: https://insights.sbomify.com/CVE-2026-97206/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97206
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97206
- OSV: https://osv.dev/vulnerability/CVE-2026-97206

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97206/
Summaries are generated and may contain mistakes; the official description above is the record.