Access of Uninitialized Pointer in Unbound - CVE-2026-42959

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Main Vulnerability Database Vulnerabilities #VU131930

Access of Uninitialized Pointer in Unbound - CVE-2026-42959

Published: May 20, 2026


Vulnerability identifier: #VU131930
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-42959
CWE-ID: CWE-824
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 use of an uninitialized pointer in the DNSSEC validator when constructing chase-reply messages for validation. A remote attacker can provide a malicious upstream reply to cause a denial of service.

Exploitation requires control of a DNSSEC-signed domain and can be triggered with a single query using a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records.


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

How to mitigate CVE-2026-42959

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-help - addressed in versions 1.11.0-22, 1.13.2-22, 1.17.1-16
unbound-debugsource - addressed in versions 1.11.0-22, 1.13.2-22, 1.17.1-16
unbound-debuginfo - addressed in versions 1.11.0-22, 1.13.2-22, 1.17.1-16
python3-unbound - addressed in versions 1.11.0-22, 1.13.2-22, 1.17.1-16
unbound - addressed in versions 1.11.0-22, 1.13.2-22, 1.17.1-16
unbound-devel - addressed in versions 1.11.0-22, 1.13.2-22, 1.17.1-16
unbound-libs - addressed in versions 1.11.0-22, 1.13.2-22, 1.17.1-16
unbound-anchor - addressed in versions 1.13.2-22, 1.17.1-16
unbound (Red Hat package) - addressed in versions 1.16.2-5.11.el8_10, 1.24.2-3.el9_8.1, 1.24.2-7.el10_2.1
python3-unbound - addressed in versions 1.16.2-9.0.1, 1.17.1-11
unbound - addressed in versions 1.16.2-9.0.1, 1.17.1-11
unbound-devel - addressed in versions 1.16.2-9.0.1, 1.17.1-11
unbound-libs - addressed in versions 1.16.2-9.0.1, 1.17.1-11
unbound-utils - update to 1.17.1-11
unbound-anchor - update to 1.17.1-11
unbound-utils - update to 1.17.1-16
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-python-debuginfo - update to 1.20.0-150600.23.16.1
unbound-munin - 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

External References

Related Security Bulletins