NLnet Labs Unbound up to 1.25.1 DNS-over-QUIC denial of service

Summaryinfo

A vulnerability was found in NLnet Labs Unbound up to 1.25.1. It has been rated as problematic. This vulnerability affects unknown code of the component DNS-over-QUIC. The manipulation leads to denial of service. This vulnerability is traded as CVE-2026-14586. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in NLnet Labs Unbound up to 1.25.1. It has been rated as problematic. This issue affects an unknown function of the component DNS-over-QUIC. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. The summary by CVE is:

In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, in DNS-over-QUIC environments, with high concurrency and under pressure, an assertion in libngtcp2 about monotonic timestamps could trigger and result in server termination and thus denial of service. When interfacing with libngtcp2, for DNS-over-QUIC support in Unbound, it is expected to use monotonic time. Unbound was using realtime instead, and in DoQ environments with high concurrency and under pressure, an assert in libngtcp2 for the quic timestamp would trigger and terminate the server.This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.

It is possible to read the advisory at nlnetlabs.nl. The identification of this vulnerability is CVE-2026-14586 since 07/03/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

The vulnerability scanner Nessus provides a plugin with the ID 330825 (Fedora 44 : unbound (2026-e495bd59ef)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.25.2 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (330825) and CERT Bund (WID-SEC-2026-2492). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Open Source Unbound

Productinfo

Vendor

• NLnet Labs

Name

• Unbound

Version

• 1.25.0
• 1.25.1

CPE 2.3info

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CPE 2.2info

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Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

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