Heap-based buffer overflow in Unbound - CVE-2026-82717

Vulnerability identifier: #VU150194

CSH Severity: High

CVSS v4: 9.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-82717

CWE-ID: CWE-122

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to a heap-based buffer overflow in the CNAME synthesis packet-buffer handling logic when processing a crafted upstream DNS response that requires max TTL rewriting. A remote attacker can send a specially crafted upstream DNS response to execute arbitrary code.

Successful code execution depends on the system configuration, compilation options, and heap memory layout.

Unbound
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
Debian Linux
SUSE Linux Enterprise High Performance Computing 15
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 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
Ubuntu
Basesystem Module
SUSE Package Hub 15
openSUSE Leap
openEuler
Fedora
python-unbound (Ubuntu package)
unbound (Ubuntu package)
libunbound2 (Ubuntu package)
python3-unbound (Ubuntu package)
libunbound8 (Ubuntu package)
unbound
python3-unbound
unbound-anchor
unbound-debuginfo
unbound-debugsource
unbound-devel
unbound-help
unbound-libs
unbound (Red Hat package)
unbound-utils
libunbound8
unbound-anchor-debuginfo
libunbound8-debuginfo
unbound-munin
libunbound-devel-mini-debuginfo
unbound-python-debuginfo
unbound-python
libunbound-devel-mini-debugsource
libunbound-devel-mini
unbound (Debian package)
Red Hat OpenShift Container Platform

Install security update from vendor's website.

Unbound - update to 1.26.1
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
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
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
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 - addressed in versions 1.13.2-28, 1.17.1-22
python3-unbound - addressed in versions 1.13.2-28, 1.17.1-22
unbound-anchor - addressed in versions 1.13.2-28, 1.17.1-22
unbound-debuginfo - addressed in versions 1.13.2-28, 1.17.1-22
unbound-debugsource - addressed in versions 1.13.2-28, 1.17.1-22
unbound-devel - addressed in versions 1.13.2-28, 1.17.1-22
unbound-help - addressed in versions 1.13.2-28, 1.17.1-22
unbound-libs - addressed in versions 1.13.2-28, 1.17.1-22
unbound (Red Hat package) - addressed in versions 1.16.2-5.14.el8_10.4, 1.24.2-3.el9_8.8, 1.24.2-7.el10_2.6
unbound-devel - addressed in versions 1.16.2-9.0.5, 1.17.1-21
unbound - addressed in versions 1.16.2-9.0.5, 1.17.1-21
unbound-libs - addressed in versions 1.16.2-9.0.5, 1.17.1-21
python3-unbound - addressed in versions 1.16.2-9.0.5, 1.17.1-21
unbound-utils - update to 1.17.1-21
unbound-anchor - update to 1.17.1-21
unbound-utils - update to 1.17.1-22
unbound - addressed in versions 1.26.1-1.fc43, 1.26.1-1.fc44, 1.26.1-1.fc45
libunbound8 - 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-anchor-debuginfo - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
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-debuginfo - 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
unbound - update to 1.26.1-150600.23.24.1
libunbound-devel-mini - update to 1.26.1-150600.23.24.1
Red Hat OpenShift Container Platform - update to 4.22.17
unbound (Debian package) - update to 1.26.1-0+deb13u1

• https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82717.txt
• https://nlnetlabs.nl/downloads/unbound/patch_CVE-2026-82717_with.diff
• https://github.com/NLnetLabs/unbound/releases/tag/release-1.26.1

• Multiple vulnerabilities in Unbound
• Fedora 45 update for unbound
• Fedora 44 update for unbound
• Fedora 43 update for unbound
• Debian update for unbound
• Red Hat Enterprise Linux 8 update for unbound
• Red Hat Enterprise Linux 10 update for unbound
• Red Hat Enterprise Linux 9 update for unbound
• openEuler 22.03 LTS SP4 update for unbound
• openEuler 24.03 LTS SP4 update for unbound
• openEuler 24.03 LTS SP3 update for unbound
• openEuler 24.03 LTS SP1 update for unbound
• Multiple vulnerabilities in Red Hat OpenShift Container Platform 4.22
• SUSE update for unbound
• SUSE update for unbound
• Anolis OS update for unbound
• Anolis OS update for unbound
• Ubuntu update for unbound