Use-after-free in Unbound - CVE-2026-97206
Published: October 21, 2026
Vulnerability identifier: #VU156695
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-97206
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service by crashing Unbound.
The vulnerability exists due to use-after-free in Unbound's DNS-over-QUIC stream cleanup when handling client-triggered QUIC path migration during multi-threaded operation. A remote attacker can trigger path migration while a pending mesh reply retains a pointer to a DoQ stream, causing the reply to dereference the stream after cleanup frees it, to crash the service.
Affected software
Unbound
How to mitigate CVE-2026-97206
Install security update from vendor's website.
Unbound - update to 1.26.2