Out-of-bounds write in Unbound - CVE-2026-81642

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Main Vulnerability Database Vulnerabilities #VU150193

Out-of-bounds write in Unbound - CVE-2026-81642

Published: September 16, 2026 / Updated: September 19, 2026


Vulnerability identifier: #VU150193
CSH Severity: High
CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-81642
CWE-ID: CWE-787
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to execute arbitrary code or cause a denial of service.

The vulnerability exists due to a buffer overflow in Unbound's DNSSEC validator when processing a DNSKEY with an owner compression pointer to its own RDATA. A remote attacker can control a malicious zone and query a vulnerable Unbound instance to execute arbitrary code or cause a denial of service.


Affected software

Unbound
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
Debian Linux
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
Anolis OS
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux Server - TUS
Ubuntu
Basesystem Module
SUSE Package Hub 15
openSUSE Leap
openEuler
Fedora
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
libunbound2 (Ubuntu package)
unbound (Ubuntu package)
python-unbound (Ubuntu package)
python3-unbound (Ubuntu package)
libunbound8 (Ubuntu package)
unbound (Red Hat package)
python3-unbound
unbound-devel
unbound
unbound-libs
unbound-utils
unbound-anchor
unbound-help
unbound-debugsource
unbound-debuginfo
libunbound8
libunbound8-debuginfo
unbound-anchor-debuginfo
unbound-munin
libunbound-devel-mini-debuginfo
unbound-python-debuginfo
unbound-python
libunbound-devel-mini-debugsource
libunbound-devel-mini
unbound (Debian package)

How to mitigate CVE-2026-81642

Install security update from vendor's website.

Unbound - update to 1.26.1
libunbound2 (Ubuntu package) - addressed in versions 1.4.22-1ubuntu4.14.04.3+esm4, 1.5.8-1ubuntu1.1+esm4, 1.6.7-1ubuntu2.6+esm5
unbound (Ubuntu package) - addressed in versions 1.4.22-1ubuntu4.14.04.3+esm4, 1.5.8-1ubuntu1.1+esm4, 1.6.7-1ubuntu2.6+esm5, 1.9.4-2ubuntu1.11+esm2, 1.13.1-1ubuntu5.16, 1.19.2-1ubuntu3.10, 1.24.2-1ubuntu2.3
python-unbound (Ubuntu package) - addressed in versions 1.4.22-1ubuntu4.14.04.3+esm4, 1.5.8-1ubuntu1.1+esm4, 1.6.7-1ubuntu2.6+esm5, 1.9.4-2ubuntu1.11+esm2
python3-unbound (Ubuntu package) - addressed in versions 1.6.7-1ubuntu2.6+esm5, 1.9.4-2ubuntu1.11+esm2, 1.13.1-1ubuntu5.16, 1.19.2-1ubuntu3.10, 1.24.2-1ubuntu2.3
libunbound8 (Ubuntu package) - addressed in versions 1.9.4-2ubuntu1.11+esm2, 1.13.1-1ubuntu5.16, 1.19.2-1ubuntu3.10, 1.24.2-1ubuntu2.3
unbound (Red Hat package) - addressed in versions 1.6.6-5.el7_9.2, 1.7.3-15.el8_4.4, 1.7.3-17.el8_6.8, 1.16.2-3.el9_2.6, 1.16.2-5.el8_8.6, 1.16.2-5.14.el8_10.4, 1.16.2-8.el9_4.3, 1.24.2-3.el9_8.8, 1.24.2-7.el10_2.6
python3-unbound - addressed in versions 1.16.2-9.0.5, 1.17.1-19
unbound-devel - addressed in versions 1.16.2-9.0.5, 1.17.1-19
unbound - addressed in versions 1.16.2-9.0.5, 1.17.1-19
unbound-libs - addressed in versions 1.16.2-9.0.5, 1.17.1-19
unbound-utils - update to 1.17.1-19
unbound-anchor - update to 1.17.1-19
unbound-anchor - update to 1.17.1-21
python3-unbound - update to 1.17.1-21
unbound - update to 1.17.1-21
unbound-utils - update to 1.17.1-21
unbound-libs - update to 1.17.1-21
unbound-help - update to 1.17.1-21
unbound-devel - update to 1.17.1-21
unbound-debugsource - update to 1.17.1-21
unbound-debuginfo - update to 1.17.1-21
unbound - addressed in versions 1.26.1-1.fc43, 1.26.1-1.fc44, 1.26.1-1.fc45
unbound-anchor - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-debuginfo - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-devel - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
libunbound8 - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
libunbound8-debuginfo - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-anchor-debuginfo - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-debugsource - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-munin - update to 1.26.1-150600.23.24.1
libunbound-devel-mini-debuginfo - update to 1.26.1-150600.23.24.1
unbound-python-debuginfo - update to 1.26.1-150600.23.24.1
unbound-python - update to 1.26.1-150600.23.24.1
libunbound-devel-mini-debugsource - update to 1.26.1-150600.23.24.1
libunbound-devel-mini - update to 1.26.1-150600.23.24.1
unbound - update to 1.26.1-150600.23.24.1
unbound (Debian package) - update to 1.26.1-0+deb13u1

External References

Related Security Bulletins