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

CVE-2026-97206 is fixed in unbound on 1 platform, first by DEBIAN-CVE-2026-97206, released October 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-97206
- Priority: High
- CVSS: 7.5 (Important)
- EPSS: 0.0033
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 21, 2026
- Weakness: Use After Free
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-97206

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | unbound Debian 13.5 (trixie) | 1.26.2-0+deb13u1 | [DEBIAN-CVE-2026-97206](https://patchblox.com/security/data/fix/linux/debian-cve-2026-97206.md) | Oct 24, 2026 |
| Linux | unbound Debian 14 | 1.26.2-1 | [DEBIAN-CVE-2026-97206](https://patchblox.com/security/data/fix/linux/debian-cve-2026-97206.md) | Oct 24, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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