Vulnerability · Published Oct 21, 2026 · Assigned by NLnet Labs

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

High 7.5

In plain English

A high-severity use-after-free in Unbound from NLnet Labs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 73.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack tooling1Public PoC

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	unbound	no fix listed	DEBIAN-CVE-2026-97206
Debian:13	unbound	1.26.2-0+deb13u1	DEBIAN-CVE-2026-97206
Debian:14	unbound	1.26.2-1	DEBIAN-CVE-2026-97206
Ubuntu:22.04:LTS	unbound	no fix listed	UBUNTU-CVE-2026-97206
Ubuntu:24.04:LTS	unbound	no fix listed	UBUNTU-CVE-2026-97206
Ubuntu:26.04:LTS	unbound	no fix listed	UBUNTU-CVE-2026-97206
Ubuntu:26.10	unbound	no fix listed	UBUNTU-CVE-2026-97206

Affected products (as reported)

Vendor	Product	Versions
NLnet Labs	Unbound	1.22.0 – before 1.26.2

Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-97206.txt vendor-advisory