Resource exhaustion in Unbound - CVE-2026-44390

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Main Vulnerability Database Vulnerabilities #VU131932

Resource exhaustion in Unbound - CVE-2026-44390

Published: May 20, 2026


Vulnerability identifier: #VU131932
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-44390
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to uncontrolled resource consumption in name compression handling for downstream replies when processing malicious upstream responses with very large RRsets whose records do not share a suffix above the root. A remote attacker can query Unbound for specially crafted contents of a malicious zone to cause a denial of service.

The issue can lock the CPU while the reply packet is being completed, leading to degraded performance before service disruption.


Affected software

Unbound
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
Debian Linux
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 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
SUSE Package Hub 15
Basesystem Module
openSUSE Leap
openEuler
Fedora
LANTIME Operating System Firmware (LTOS)
unbound (Ubuntu package)
unbound-libs
unbound-help
unbound
python3-unbound
unbound-debuginfo
unbound-debugsource
unbound-devel
unbound-anchor
unbound (Red Hat package)
unbound-utils
unbound-anchor-debuginfo
libunbound8-debuginfo
libunbound8
unbound-munin
unbound-python-debuginfo
libunbound-devel-mini-debuginfo
unbound-python
libunbound-devel-mini
libunbound-devel-mini-debugsource
unbound (Debian package)

How to mitigate CVE-2026-44390

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, 1.13.2-23, 1.17.1-17
unbound-help - addressed in versions 1.11.0-23, 1.13.2-23, 1.17.1-17
unbound - addressed in versions 1.11.0-23, 1.13.2-23, 1.17.1-17
python3-unbound - addressed in versions 1.11.0-23, 1.13.2-23, 1.17.1-17
unbound-debuginfo - addressed in versions 1.11.0-23, 1.13.2-23, 1.17.1-17
unbound-debugsource - addressed in versions 1.11.0-23, 1.13.2-23, 1.17.1-17
unbound-devel - addressed in versions 1.11.0-23, 1.13.2-23, 1.17.1-17
unbound-anchor - addressed in versions 1.13.2-23, 1.17.1-17
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 - update to 1.17.1-17
unbound-anchor-debuginfo - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1
unbound-devel - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1
libunbound8-debuginfo - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1
unbound-anchor - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1
unbound-debugsource - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1
libunbound8 - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1
unbound-debuginfo - addressed in versions 1.20.0-150100.10.25.1, 1.20.0-150600.23.16.1
unbound-munin - update to 1.20.0-150600.23.16.1
unbound-python-debuginfo - update to 1.20.0-150600.23.16.1
unbound - update to 1.20.0-150600.23.16.1
libunbound-devel-mini-debuginfo - update to 1.20.0-150600.23.16.1
unbound-python - update to 1.20.0-150600.23.16.1
libunbound-devel-mini - update to 1.20.0-150600.23.16.1
libunbound-devel-mini-debugsource - update to 1.20.0-150600.23.16.1
unbound (Debian package) - update to 1.22.0-2+deb13u3
unbound - addressed in versions 1.25.1-1.fc43, 1.25.1-1.fc44, 1.25.2-1.fc43

External References

Related Security Bulletins