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Fencer Vulns
medium 5.9

CVE-2026-14586 json

Assertion in libngtcp2 when under pressure in high concurrency DNS-over-QUIC environments

published 2026-07-22 3 mo ago modified 2026-10-24 16 d ago also EUVD-2026-47662

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

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.

Patch / fix

  • NLnet Labs Unbound 1.25.2
  • unbound Debian 13 1.26.1-0+deb13u1
  • unbound Debian 14 1.25.2-1

debian advisories DEBIAN-CVE-2026-14586

  • unbound hummingbird 1 1.25.2-0.1.hum1
  • unbound-libs hummingbird 1 1.25.2-0.1.hum1
  • unbound-munin hummingbird 1 1.25.2-0.1.hum1
  • unbound-utils hummingbird 1 1.25.2-0.1.hum1
  • unbound-anchor hummingbird 1 1.25.2-0.1.hum1
  • unbound-dracut hummingbird 1 1.25.2-0.1.hum1
  • python3-unbound hummingbird 1 1.25.2-0.1.hum1

red hat advisories RHSA-2026:43588

  • unbound Linux Micro 6.0 1.25.2-1.1
  • unbound Linux Micro 6.1 1.25.2-slfo.1.1_1.1
  • unbound SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 1.25.2-160000.1.1

suse advisories SUSE-SU-2026:23360-1SUSE-SU-2026:23349-1SUSE-SU-2026:23050-1SUSE-SU-2026:23215-1SUSE-SU-2026:23226-1

  • unbound openSUSE Leap 16.0 1.25.2-160000.1.1
  • unbound openSUSE Tumbleweed 1.25.2-1.1

opensuse advisories openSUSE-SU-2026:21550-1openSUSE-SU-2026:11380-1

  • unbound Azure Linux 3.0 1.25.2-1

azure linux advisories AZL-92967

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-14586 updated cvss 5.9

unbound: Unbound: Denial of Service via assertion failure in DNS-over-QUIC environments

  • Red Hat Enterprise Linux 9 unbound, unbound-libs, unbound-dracut, python3-unbound Red Hat Enterprise Linux 10 unbound Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images unbound 1.25.2-0.1.hum1, unbound-libs 1.25.2-0.1.hum1, unbound-munin 1.25.2-0.1.hum1, unbound-utils 1.25.2-0.1.hum1, unbound-anchor 1.25.2-0.1.hum1, unbound-dracut 1.25.2-0.1.hum1, +1 more
    fixed: vendor fix RHSA-2026:43588
  • Red Hat Enterprise Linux 6 unbound, unbound-libs, unbound-python Red Hat Enterprise Linux 7 unbound, unbound-libs, unbound-python Red Hat Enterprise Linux 8 unbound, unbound-libs, python3-unbound
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • NLnet Labs Unbound

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.