Improper control of a resource through its lifetime in Unbound - CVE-2026-40622

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Main Vulnerability Database Vulnerabilities #VU131925

Improper control of a resource through its lifetime in Unbound - CVE-2026-40622

Published: May 20, 2026


Vulnerability identifier: #VU131925
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-40622
CWE-ID: CWE-664
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to extend the ghost domain window.

The vulnerability exists due to improper handling of cached parent-side referral NS records in Unbound when processing NS queries for a ghost zone. A remote attacker can control a ghost zone and trigger replacement of an expired parent-side referral NS rrset with the child-side apex NS rrset to extend the ghost domain window.

In configurations with 'harden-referral-path: yes', no client NS query is required because the resolver performs that query implicitly.


Affected software

Unbound
Debian Linux
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro
Anolis OS
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
FreeBSD
Ubuntu
Basesystem Module
SUSE Package Hub 15
openSUSE Leap
openEuler
Fedora
LANTIME Operating System Firmware (LTOS)
unbound (Ubuntu package)
unbound-libs
unbound-help
unbound-devel
unbound-debugsource
unbound-debuginfo
python3-unbound
unbound
unbound-anchor
unbound (Red Hat package)
unbound-utils
libunbound8
libunbound8-debuginfo
unbound-anchor-debuginfo
unbound-python-debuginfo
unbound-munin
libunbound-devel-mini-debugsource
libunbound-devel-mini-debuginfo
unbound-python
libunbound-devel-mini
unbound (Debian package)

How to mitigate CVE-2026-40622

Install security update from vendor's website.

Unbound - update to 1.25.1
LANTIME Operating System Firmware (LTOS) - update to 7.10.012
unbound (Ubuntu package) - addressed in versions 1.4.22-1ubuntu4.14.04.3+esm3, 1.5.8-1ubuntu1.1+esm3, 1.6.7-1ubuntu2.6+esm4, 1.9.4-2ubuntu1.11+esm1, 1.13.1-1ubuntu5.15, 1.19.2-1ubuntu3.8, 1.22.0-2ubuntu2.3, 1.24.2-1ubuntu2.1
unbound-libs - addressed in versions 1.11.0-23, 1.11.0-26, 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
unbound-help - addressed in versions 1.11.0-23, 1.11.0-26, 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
unbound-devel - addressed in versions 1.11.0-23, 1.11.0-26, 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
unbound-debugsource - addressed in versions 1.11.0-23, 1.11.0-26, 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
unbound-debuginfo - addressed in versions 1.11.0-23, 1.11.0-26, 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
python3-unbound - addressed in versions 1.11.0-23, 1.11.0-26, 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
unbound - addressed in versions 1.11.0-23, 1.11.0-26, 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
unbound-anchor - addressed in versions 1.13.2-23, 1.13.2-26, 1.17.1-17, 1.17.1-20
unbound (Red Hat package) - addressed in versions 1.16.2-5.12.el8_10, 1.24.2-3.el9_8.2, 1.24.2-7.el10_2.2
unbound-libs - update to 1.16.2-9.0.2
unbound-devel - update to 1.16.2-9.0.2
unbound - update to 1.16.2-9.0.2
python3-unbound - update to 1.16.2-9.0.2
unbound-utils - addressed in versions 1.17.1-17, 1.17.1-20
unbound-debuginfo - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
libunbound8 - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound-debugsource - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound-anchor - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
libunbound8-debuginfo - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound-devel - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound-anchor-debuginfo - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound-python-debuginfo - addressed in versions 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound-munin - addressed in versions 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
libunbound-devel-mini-debugsource - addressed in versions 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound - addressed in versions 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
libunbound-devel-mini-debuginfo - addressed in versions 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound-python - addressed in versions 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
libunbound-devel-mini - addressed in versions 1.20.0-150600.23.16.1, 1.25.2-150600.23.19.1
unbound (Debian package) - addressed in versions 1.22.0-2+deb13u3, 1.26.1-0+deb13u1
unbound - addressed in versions 1.25.1-1.fc43, 1.25.1-1.fc44, 1.25.2-1.fc43

External References

Related Security Bulletins