TI-2026-78586 Aliases CVE-2026-97206 GHSA-jc7q-6h55-rr57

Unbound DoQ path migration use-after-free on multi-threaded deployments

LOW 39CWE-416Published 2026-10-21 · Updated 2026-10-29

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-416 and the CVSS impact.

Summary

NLnet Labs Unbound from 1.22.0 before 1.26.2 is affected. A DNS-over-QUIC (DoQ) lifetime bug (CWE-416) lets a remote DoQ client trigger a use-after-free when running multi-threaded. A client-triggered QUIC path migration frees a DoQ stream while a pending mesh reply still holds a pointer to it, and the stale pointer is dereferenced when the reply completes, causing a crash. An unauthenticated remote attacker can crash the server without privileges or user interaction.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00334 26th percentileScored 2026-11-07

Fix Fixed Unbound (NLnet Labs): 1.26.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
NLnet Labs	Unbound	1.22.0 to before 1.26.2	1.26.2	Patch available	CNA

Unbound VendorNLnet Labs Affected 1.22.0 to before 1.26.2 Fixed in 1.26.2 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:nlnetlabs:unbound::::::::	—	—	NLNETLABS

cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* Versions — — ·NLNETLABS

Remediation

Upgrade NLnet Labs Unbound to version 1.26.2, which is the fixed version.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Fix · CNA Unbound (NLnet Labs) Fixed in 1.26.2

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

Release · 2026-10-21
NLnet Labs Unbound 1.26.2
5 records Highest priority Priority LOW 5 LOW
Other records, highest priority first
- TI-2026-78584 Unbound resolver lacks aggregate limit on DNS compression pointersPriority LOW 30
- TI-2026-78546 Unbound NXDOMAIN denial for island trust anchor under insecure parentPriority LOW 28
- TI-2026-78614 Cache side-channel in NLnet Labs Unbound leaks upstream source portPriority LOW 23
Show all 5 records →

Timeline

2026-10-21 Threatist record created from CVE-2026-97206
2026-10-21 Alias added: GHSA-jc7q-6h55-rr57
2026-10-22 Priority changed: MEDIUM → LOW
2026-10-29 CISA SSVC decision points changed

References

Advisory 1

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

TI-2026-25690 Possible arbitrary code execution during DNSSEC validation CVSS 4.0CRITICAL 9.1
TI-2026-56302 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY CVSS 4.0CRITICAL 9.1
TI-2026-31146 Crash during DNSSEC validation of malicious content CVSS 4.0HIGH 8.7
TI-2026-31135 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options CVSS 4.0HIGH 8.7
TI-2026-36436 Routinator crashes on specifically crafted RRDP XML files CVSS 4.0HIGH 8.7
TI-2026-36433 Routinator exits when accepting an incoming HTTP or RTR connection fails CVSS 4.0HIGH 8.7

See all 96 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences