DNS-over-QUIC Lifetime Bug in NLnet Labs Unbound
CVE-2026-97206

7.5HIGH

Key Information:

Vendor

Nlnet Labs

Status
Unbound
Vendor
CVE Published:
21 October 2026

What is CVE-2026-97206?

A vulnerability in NLnet Labs Unbound affects versions from 1.22.0 to 1.26.1, where a DNS-over-QUIC (DoQ) lifetime bug can be exploited by a remote DoQ client. This issue arises under multi-threaded conditions, particularly when a client triggers QUIC path migration. During stream and connection cleanup, a mesh reply may hold a reference to an in-progress DoQ stream, which, if cleaned up prematurely, can result in dereferencing a stale pointer when the reply completes. This vulnerability poses a risk of causing crashes in the Unbound application.

Affected Version(s)

Unbound 1.22.0 < 1.26.2

References

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

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Kunta Chu (Tsinghua University)
Jianjun Chen (Tsinghua University)
.